A Method for the Preparation of Highly Oriented MAPbI3 Crystallites

Subscriber access provided by University of Sunderland

Article

A Method to Prepare Highly Oriented MAPbI3 Crystallites for High Efficiency Perovskite Solar Cell to Achieve 86% Fill Factor Chien-Hung Chiang, and Chun-Guey Wu ACS Nano, Just Accepted Manuscript • DOI: 10.1021/acsnano.8b05731 • Publication Date (Web): 03 Oct 2018 Downloaded from http://pubs.acs.org on October 3, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

A Method to Prepare Highly Oriented MAPbI3 Crystallites for High Efficiency Perovskite Solar Cell to Achieve 86% Fill Factor

Chien-Hung Chianga,b, Chun-Guey Wua,b,*,

a

Research Center for New Generation Light Driven Photovoltaic modules, National Central University.

b

Department of Chemistry, National Central University, Jhong-Li, 32001, Taiwan, ROC.

E-mail address of Professor C. G. Wu: [email protected]

1

ACS Paragon Plus Environment

ACS Nano 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Graphical table of content

Controlled crystallization and H2O post treatment were used to prepare highly ordered, large grain MAPbI3 film for p-i-n PSC to achieve 21.1% efficiency.

Keywords: Perovskite, inverted cell, anti-solvent, gas blowing, post treatment.

2


Page 2 of 42

Page 3 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

Photovoltaic cell based on organic-inorganic hybrid lead halide perovskite is a hot research subject for both scientists and engineers in the past several years.1-12 The quality of the perovskite absorber is the key parameter for the photovoltaic performance of the corresponding cell.9 It was shown that the cell based on perovskite film containing large grains (multi-crystalline particles) has higher efficiency and better long-term stability than that based on the film with small granules.9,13 The boundaries of the multi-crystalline grains/particles were regarded as the defects sites which cause the energy loss via non-radiative recombination, decreasing the efficiency of the cell.14,15 Many innovative approaches had been developed to improve the quality of perovskite film since the first report which using a simple one-step spin-coating to prepare MAPbX3 (X: I, Br) films.10 Those approaches include using various two-step fabrication method,7,16-21 varying the solvents22-24 and temperature25 of the perovskite precursor solution, forming the solvent coordinated intermediates,26 adding additive in the precursor solution27-34 and post treatment of the perovskite film.22,33-38 The detail mechanisms for those approaches may not be totally understood. Nevertheless, be able to control the perovskite nucleation and growth on various substrates is the key factor to prepare high-quality film with high crystallinity, large grains as well as very compact and flat.39 Therefore if an effective way to manipulate the nucleation and growth of perovskite can be identified, film with optimal morphology/crystallinity can be made and then high-efficiency perovskite solar cells can be replicated easily. Nucleation is known to be a stochastic process: even in two very similar systems nucleation will start at different times.40 Crystalline perovskite film grown on a substrate can be regarded as a heterogeneous nucleation process (nucleation occurs on a substrate) which is very sensitive to a large number of factors, such as concentration, composition and solvent of the precursor solution,22-34,41,42 deposition temperature15,25 3


ACS Nano 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 42

chemical identity of the substrate43 and so on. Therefore, if the crystallization mechanism of perovskite on a substrate under spin coating was known, high quality films can be made. The LaMer graph,44 widely used to explain the nucleation and grain growth processes, can be adopted to describe the formation of perovskite film on a substrate from its precursor solution via spin-coating.45 In the LaMer model, upon drying, perovskite solution reaches a concentration called critical concentration (CC), many nuclei generate and then start to grow. As long as the concentration of the solution is above the CC, new nuclei continuously generate and grow as well as old nuclei. When the solvent evaporation rate is slower than the consumption of solute due to the crystal nucleation and growth, the concentration decreases to below CC and the nucleation stopped but the nuclei continuously grow until the solution reaches the saturation concentration (SC). The concentration increases again to above CC upon continuous solvent evaporation, the nucleation and growth start again and then both processes stop when the perovskite concentration below SC. The cycle repeated until all solvent molecules evaporated totally. Repeating nucleation and growth cycles caused the perovskite crystals aggregating in a three-dimension (3D) matter, resulting in rough film. If the solvent in the precursor solution can be removed/exchanged very fast, nucleation occurs only once, smooth perovskite film can be fabricated although the grains of the film may not be large, due to the fast nucleation. Solvent-solvent extraction (SSE) or called anti-solvent engineering (ASE)19,46 is a typical example based on rapid solvent exchanging to deposit a dense, uniform and smooth perovskite film in the one-step spin coating process. On the other hand, vacuum

flash–assisted

deposition,47

gas-assisted preparation,48

gas

blowing

fabrication,49 soft-cover deposition,50 gas pumping,51,52 and gas-flow-induced gas pump (GGPM)49,53 methods are some examples for preparing high quality perovskite film via fast solvent (of the precursor solution) evaporation. These modified one-step 4


Page 5 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

solution processes47-49,53 (based on fast solvent evaporation to induce rapid nucleation) was successfully adopted to fabricate large-area, good quality film for perovskite mini-modules.47,53 Nevertheless, better quality perovskite film still needs to enhance the photovoltaic performance of the corresponding solar cell. In this paper, we report a creative method, which combining the anti-solvent engineering (induce rapid crystallite precipitation), gas blowing (orientates the grains and brings them closer), and H2O post treatment (grain boundaries mending), to prepare flat dense MAPbI3 film having highly ordered perovskite large grains. The inverted cell based on this high quality perovskite film achieves the power conversion efficiency (PCE) of 21% with extremely large FF value of 86%. Furthermore, the same method was also successfully used to prepare large area, good quality MAPbI3 film for perovskite min-module (active area of 11.25 cm2 on a 5 cm x 5 cm substrate) to realize the PCE over 16% with very high FF of 80%. To test the feasibility of this method toward other perovskite materials, the same methods were used to prepare FAxMA1-xPbI3-xBrx films for the inverted PSC. The merits of combining the anti-solvent engineering, gas blowing, and H2O post treatment are well revealed.

RESULTS and DISCUSSION The steps for preparing compact MAPbI3 film with large, highly ordered grains via anti-solvent engineering (ASE) and gas blowing (GB), followed by post H2O treatment are illustrated in Figure 1. During the one-step spin coating process right after the anti-solvent (chlorobenzene, CB) was applied at the last 2 seconds of spin, a N2 gas was blew on the wet film for 30 seconds. After the film was heated at 100oC for 5 min, it was put back to the spin coater. 100 µL CB containing various amount of H2O was added on the film under the fast spin of 9000 rpm for 30 sec, then annealed the film again at 100oC for 5 min. For increasing the solvent evaporation rate to 5


ACS Nano 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 42

promote fast nucleation, hot (60oC) MAPbI3/DMF precursor solution was used. To show the merit of gas blowing, four film preparation ways were used to make MAPbI3 films in this study: simple one-step spin coating (SSC); one-step spin coating under continuous gas blowing (CGB); one-step spin coating with anti-solvent engineering (ASE); and combining anti-solvent engineering and gas blowing (ASE/GB) in an one-step spin coating. SEM images of the prevoskite films prepared with four difference methods were displayed in Figure 2. When a simple one-step spin coating was used, drying of the film during spin-coating is quite slow due to high boiling point (153oC) of solvent DMF. Consequently, nucleation and crystal growth occur several cycles as LaMer model stated.44 The resulting perovskite film (SSC) has a 3D (three-dimension) dendritic like (or nano fibrous) aggregation (see Figure 2(a)). Gas blowing (increasing the solvent evaporation rate) or anti-solvent engineering (reducing the solubility of MAPbI3) makes the perovskite solution reaching the critical concentration (CC) very fast, therefore a large number of nuclei burst before extended crystal growth occurs. As a result, compact and flat provskite films (CGB and ASE) with rather uniform grain (multi-crystalline particles) size (Figure 2(b) and (c)) were made.

SEM images

also reveal that CGB film prepared under continuous gas blowing has larger grains compared to ASE film fabricated by anti-solvent engineering. It seems that gas blowing during the spin coating process is an effective way to prepare flat MAPbI3 film with large grains probably due to can disperse the precursor solution evenly on the substrate.54 Combining the anti-solvent treating and gas blowing the resulting ASE/GB film contains some large grains, however, the grain size is not homogeneous, lots of small grains are also formed. Grazing-incidence wide angle X-ray diffraction (GIWAXD) patterns of the perovskite films prepared with the four methods are displayed in Figure 3 (the 6


Page 7 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

original 2D data were displayed in Figure S1a of the electronic supporting information (ESI)). The (110) peak intensity of CGB and ASE/GB films is much stronger than those of SSC and ASE films. However the intensity of one single diffraction peak cannot be used as the only parameter to identify the difference in the crystallinity unless the degree of the prefer orientation of the films is known. As the data shown in the inert of Figure 3, the intensity of the (200) diffraction peaks for all films is very weak but the difference is visible. Therefore the (110)/(200)55,56 intensity ratio is used for indicating the prefer orientation of MAPbI3 films. The ratios of the peaks intensity are 7.6, 32, 260 and 970, for SSC, ASE, CGB and ASE/GB films, respectively. MAPbI3 films (CGB and ASE/GB) deposited on PEDOT:PSS by spin-coating under N2 gas blowing show significantly higher prefer orientation than the other two films. The sharper diffraction peak of CGB and ASE/GB films also indicated the average crystal size of both films is larger than those of SSC and ASE films. The full width at half maximum (FWHM) of the (110) peak decreased from 0.36° for ASE to 0.32° for ASE/GB, reflecting the expansion of the mean size of perovskite crystallites from 25 to 27.8 nm, although they are not actual mean crystallites sizes of the films due to the instrument line-broadening. These results indicate that gas blowing during spin coating process can simultaneously increase the crystallinity, orientation and crystalline domain as well as the grain size (from SEM images shown in Figure 2) of MAPbI3 film. 2D GIWAXD is a powerful technique for determining the film crystallinity as well as the orientation of the crystallites. The highly preferred orientation of the pervoskite film prepared under gas blowing was also confirmed by the pole plots57 (constructed from the 2D diffraction patterns) illustrated in Figure S1b, ESI. Highly oriented, long-range (millimeter scale, the size (1 mm) of the X-ray beam) ordered MAPbI3 film prepared by combining the anti-solvent engineering and gas blowing 7


ACS Nano 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

during the spin coating process was clearly revealed. The order of the crystallites on the film is very homogeneous: we have probed 20 points on ASE/GB film and the intensity ratios of (110)/(200) are almost the same. The I-V curves (in the screen the MAPbI3 fabrication methods, I-V curves of the cells measured only under negative bias to compare quickly the difference in the photovoltaic performance) of the inverted cells based on the four types MAPbI3 films with the cell architecture of ITO/PEDOT:PSS/MAPbI3/C60/BCP/Ag are shown in Figure S2, ESI and the photovoltaic parameters are summarized in Table 1. The inverted cell based on ASE/GB film has the highest power conversion efficiency (PCE) amongst the MAPbI3 films prepared with different methods but its PCE is only 15.07% and all photovoltaic parameters are smaller than the high efficiency inverted PSC we reported previously.36 This may be due to the grain size of ASE/GB film is small and inhomogeneous: the largest size is ca. 500 nm and lots of small (< 200 nm) grains are also present. To further enhance the photovoltaic performance of MAPbI3 film, high concentrations of the precursor solutions were used to make ASE/GB films and the photovoltaic parameters of the resulting inverted cells are also listed in Table 1 (the corresponding I-V curves were displayed in Figure S3, ESI). The best performance film (ASE/GB-1.35) was obtained when 1.35 M hot MAPbI3/DMF solution was used nevertheless the efficiency of the corresponding cell is only enhanced to 17.0%.

SEM picture displayed in Figure 4 reveals that the surface

morphology of ASE/GB-1.35 film is similar to that of ASE/GB film prepared at low concentration (1.15 M) (see Figure 2). Many grains with the size less than 200 nm are still present, but the film thickness increases to ca. 470 nm (ASE/GB film has the thickness of ca. 400 nm). Further increasing the concentration of MAPbI3/DMF solution, rough film was obtained due to perovskite crystals precipitate before the spinning starts. It seems that increases the concentration of the precursor solution 8


Page 8 of 42

Page 9 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

cannot enlarge the grains of the resulting spin-coated film. Therefore for fabricating perovskite film with large grains to improve the photovoltaic performance,13 post treatment of the film is carried out. Post solvent treatment34-38,58,59 of perovskite film was a known strategy to enlarge its grain size. In general, post solvent annealing was performed by passing the solvent vapour to the perovskite film to rebuild the grain boundaries or to mend the defects/rifts within the grain, both leading to the formation of larger grains with fewer defects after heating. However, we found that the vapour pressure of the solvent and annealing time should be controlled precisely for improving the quality of perovskite film.36 For the purpose of commercializing the technique, a user friendly, large throughput and reproducible post treatment method is needed. On the other hand, organic-inorganic hybrid lead halide has an ionic characteristic which is very sensitive to H2O: its structure will be decomposed60 or formed non-active hydrated structures61,62 by the moisture. Perovskite will also be dissolved in H2O totally when the film was dipped in water for several minutes.36 Nevertheless, H2O can react with perovskite to form continuous smooth film by so called dissolution and recrystallization process.35,36,57-65 Therefore to take the advantages of H2O, more creative method needs to be developed. Here the post film treatment was carried out by dissolving a small amount of H2O in an anti-solvent (CB) of MAPbI3 and apply the H2O/CB mixture on the ASE/GB-1.35 film during fast (9000 rpm) spinning for 30 sec, followed by heating at 100oC for 5 min to remove the solvent. When very small amount of H2O contacts with perovskite film, only the rifts or surface of the perovskite grains were reacted with H2O to form movable water-rich phase (may be is the hydrated perovskite (reported by Aurélien et al.) mixed with H2O (or trace amount of DMF)60 and fill in the grain boundaries or the pin-hole on the grains. Upon heating, the water-rich phase convert back to MAPbI3, fill the pin-hole or the boundaries of the 9


ACS Nano 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

small grains to form big grains. SEM micrographs of the post treated films, ASE/GB-x (ASE/GB-x means ASE/GB-1.35 film treated with CB containing x volume ratio of H2O) are displayed in Figure 4. Post H2O/CB treatment does increase the grain size of MAPbI3 film. However when high concentration of H2O (in H2O/CB) was used, the resulted film has some holes on it, which harms its photovoltaic performance. When 1.0% H2O/CB was used for the post film treatment, high quality MAPbI3 film with the grain size up to 1.5 µm was obtained. The cross section SEM images (displayed in Figure S4, ESI) of ASE/GB-1% film evidence that the film with the lateral size of the grains equal to the film thickness and has a good contact with PEDOT:PSS hole transporting layer. It is very dense and the flatness of the film expends to several micrometers. The thickness of the film estimated from the cross-section image is ca. 470 nm (consistent with the value measured with the depth-profile meter) which is close to the optimal value (500 nm) we learned for MAPbI3 film used in the inverted perovskite solar cell. GIWAXD patterns (Figure S5, ESI) disclose that H2O/CB treated ASE/GB-x films are also highly oriented, the intensity and FWHM of the (110) peak of all films is also very close to that of film (ASE/GB-1.35) before H2O/CB post treatment. Interestingly, the intensity and FWHM of (110) peak of ASE/GB-1.35 did not change, although the (200) diffraction peaks (displayed in the insert of Figure S5 (ESI)) become stronger after H2O/CB post treatment. XRD dada indicates that the total crystalinity of ASE/GB-1.0% is higher than that of ASE/GB-1.35 film. The intensity of the (200) peak is much weaker ( 2.0 µm) of VPsk-0.5 film36 or maybe the absorber layer is not thick enough. If the grain size and thickness of the highly ordered MAPbI3 film can be enlarge further (ultimately to be a single crystal film with an optimal thickness), inverted perovskite solar cell with the efficiency higher than 21% is expectable. High FF value is very important for up scaling the cell area for the practical application. For an inverted perovskite solar cell with the architecture of ITO/PEDOT: PSS/Perovskite/C60/BCP/Ag, the FF depends substantial on the quality of perovskite film. If a strategy for fabricating high quality perovskite film was developed, it can be adopted to fabricate large-area film for the perovskite module. We fabricate the perovskite mini-module on a 5 cm x 5 cm substrate using the pattern designed previously.36 The p-i-n MAPbI3 mini-module (containing 5 cells in a series circuit with the active area of 45 mm x 5 mm for each cell) exhibits high PCE up to 16%. The I-V curves of the min-module at different scan directions and scan delay times are shown in Figure 6 and the corresponding photovoltaic parameters are summarized in Table S1, ESI. Gas blowing during spin coating process is a very important step for preparing highly oriented MAPbI3 film. Blowing a controllable amount of gas through the solution or wet MAPbI3 particles on substrate is an important step in this study. In CGB method blowing a gas can disperse the solution even in the substrate and increase the solvent evaporation rate to reduce the solubility of MAPbI3 in DMF (solvent of the precursor solution), therefore nucleation occurs very fast and evenly. Large amount of nuclei produced at a short time, suppressing the 3D growth, resulting in a flat and compact film. In general dripping an anti-solvent to the wet film during spin-coating need sophisticated technique due to the anti-solvent dripping may have a radial gradient in oversaturation, causing the inhomogeneous nucleation/growth of the 14


Page 14 of 42

Page 15 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

perovskite grains, result in inhomogeneous/rough perovskite film. Therefore blowing a gas through the substrate right after adding anti-solvent to make ASE/GB film has two possible positive effects: to evenly disperse the wet grains to make flat film, to increase the grain size of the film by increasing the grains growth rate or push the grains closer to each other as illustrated in Figure 7. However, due to the eruption nucleation and growing, the grain size of ASE/GB film is small and inhomogeneous (see Figure 2). Therefore a H2O/CB solution was used for as a post treating agent applying to MAPbI3 film under fast spinning. When a proper H2O concentration (in this study is 1.0%) in H2O/CB is used for the post treatment, H2O dissolve the rifts and surface of the perovskite grains to form a movable water-rich phase and fill in the grains boundaries.36 After heating at 100oC for 5 min, the H2O evaporates and the grain size increases by merging two or more small grains. The methods reported here is also feasible to prepare other mixed-cation or mixed-halide perovskite films for high-efficiency PSC. The I-V curves of the inverted cells based on FA0.85MA0.15Pb (I0.85Br0.15)3 (the best stoichiometry we found in our regular perovskite solar cell)72 films prepared with five different methods (SSC, CGB, ASE, ASE/GB ,and ASE/GB plus H2O post treatment, at the same conditions as those used to make MAPbI3) were illustrated in Figure 8 and the corresponding photovoltaic parameters were listed in Table S2, ESI. The same trend was found in both MAPbI3 and FA0.85MA0.15Pb(I0.85Br0.15)3 films. Without detailed optimizing the device fabrication parameters, the PCS of the inverted cell based on ASE/GB-1.0% is already up to 18%.

Conclusion In conclusion, we reported a method to prepare high quality MAPbI3 film by combining the anti-solvent engineering and gas blowing, followed by H2O post 15


ACS Nano 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 42

treatment. The resulting dense ASE/GB-1.0% film containing large grains is highly orientated with the long rang order in mm scale. Inverted perovskite solar cell based on the high quality ASE/GB-1.0% film achieves the PCE of 21.06% with remarkable high FF of 86% and very stable. The same method was used to fabricate FA0.85MA0.15Pb (I0.85Br0.15)3 and large area MAPbI3 film for mini-module with an active area of 11.25 cm2 to reach the efficiency of 18.3% and 16%, respectively. The strategy for enhancing the nucleation rate, suppressing the 3D nuclei growth and arranging the perovskite crystallites is the key to prepare highly oriented MAPbI3 perovskite film. Furthermore, post solvent treatment has been used to enlarge the grain size of perovskite film. Nevertheless, to obtain high quality film, the solvent vapour pressure and treating time should be controlled precisely. In this paper, we introduced a simple, fast and reproducible way to further enlarge MAPbI3 grains via H2O/CB post treatment under fast spinning. Be able to prepare large area, high quality perovskite film with a user friendly and reproducible way to achieve good photovoltaic performance pushes the perovskite solar cell one step further toward commercialization.

Experimental section: Chemicals and physicochemical studies: The chemicals were obtained from the commercial resources and used as received unless specified. CH3NH3I (MAI) was synthesized by the same method as published in the literature.73 GIWXRD data were collected in the 2θ of 5 ~ 50 degree on a Brucker powder diffractometer (D8 Discover) using Cu Kα1 radiation equipped with a 2D detector. UV/Vis and PL spectra were recorded by the Cary 300 Bio spectrometer and Hitachi F-7000 fluorescence spectrophotometer, respectively at room temperature. Scanning Electron Micrograph (SEM) was performed with a Hitachi S-800 microscopy at 15 KV. 16


Samples (surface

Page 17 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

and cross-section of the film) for SEM imaging were mounted on a metal stub with a piece of conducting tape then coated with a thin layer of gold film to avoid charging. The cross section SEM image was used for estimating the film thickness and observing the interface contact between each layer of the cell. The thickness of the perovskite films was also measured with a depth-profile meter (Veeco Dektak 150, USA). Five lines on the 1.0 cm x 1.0 cm film were made by carefully scratching with a tip and the average height between the hills and valleys is used to represent the film thickness. The nano-second time-resolved photoluminescence (TRPL) spectra were performed with an optical-microscope-based system (UniRAM, Protrustech). The average power, wavelength, pulse duration, and repetition rate of the excitation are 20

µW, 405 nm, 150 ps, and 20 MHz, respectively. The lifetime of the excitons (or charge recommendation rate) can be resolved by fitting the normalized time-dependent photoluminescence using a 2-constant exponential decay function using the follow equation as we reported previously.68

I PL = ANR exp(−t / τ NR ) + AR exp( −t / τ R ) The carrier mobility was calculated from the dark current-voltage (I–V) characteristics of the hole-only device, following the standard space charge-limited current (SCLC) model using the Mott-Gurney law.14,74 The carrier diffusion length (LD) of the cells was calculated by combining the carrier life-time with the mobility using the equation of LD = (µτPLkBT/e) 1/2 (where µ is the mobility of the cell, τPl is the average exciton lift-time (calculated with the statistical definition of τPl equal to [Σ(Aiτi)2/ΣAiτi]75 in which appear lifetimes τi and corresponding amplitudes Ai of each component, kB is Boltzmann’s constant and T is the sample’s temperature) reported by Bakr69 et al. Device Fabrication and Photovoltaic Performance Measurements. The cells

17


ACS Nano 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

and mini-modules (with the active area of 0.10 ~ 11.25 cm2) were fabricated using an one-step spin coating combined with anti-solvent (CB) engineering under continuous N2-gas blowing followed by H2O/CB post treatment. The concentration of MAPbI3 (or FA0.85MA0.15Pb (I0.85Br0.15)3) precursor solutions is 1.15 ~ 1.45 M (or 1.4 M) prepared by dissolving equal mole of PbI2 and MAI in DMF and stirred overnight, then heating to 60oC for 2 hours before applying on the substrate for spin coating. To fabricate an inverted perovskite solar cell, PEDOT:PSS was first spin-coated on a patterned ITO (the back side of the ITO glass was coated a layer (ca. 100 nm) of LiF film as an anti-reflection layer) at 5000 rpm for 50 sec from an aqueous dispersion (AI4083, 1.3~1.7 wt% of PEDOT:PSS) purchased from H.C. Stark Baytron P and then annealed at 140oC for 10 min and cool to room temperature to be a hole transporting layer. Four ways were used to deposit perovskite film, 45 µL of hot (60oC) MAPbI3/DMF (or FA0.85MA0.15Pb (I0.85Br0.15)3 in DMF:DMSO = 6:4 (V/V)) solution was spin-coated on the top of PEDOT:PSS coated ITO substrate at spin rate of 4500 rpm for 15 sec (simple spin coating, SSC). Or similar to the SSC method except at the last 2 second of the spinning, 45 µL Chlorobenzene (CB) (for preparing FA0.85MA0.15Pb (I0.85Br0.15)3, 70 µL CB was used) was added on the film as an anti-solvent (anti-solvent engineering, ASE). Or similar to the SSC method except N2 gas was blew (5 L per minute) continuously at the side (about 10 cm away from the gas source) of the substrate during spin coating process (CGB) or combining the anti-solvent engineering and gas blowing (flow rate is 15 L per minute and the distance between the gas source and substrate is ca. 10 cm) right after the anti-solvent dripping (ASE/GB). The resulting perovskite film was heated at 100oC for 5 min (for FA0.85MA0.15Pb (I0.85Br0.15)3, the heating temperature and time are 150oC and 10 min, respectively) The heated treated ASE/GB film was then undergone post film treatment by adding 100 µL H2O containing CB (the volume ratios of H2O/CB is 0.001, 0.01 18


Page 18 of 42

Page 19 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

and 0.1 and mixed very well by ultra-sonication) on its surface at the first 10 seconds of the spin (spin rate: 9000 rpm; spin time: 30 sec). The result film was thermal annealed again at 100oC for 5 min (150oC and 10 min for FA0.85MA0.15Pb (I0.85Br0.15)3 film). Acceptor layer was prepared by thermally evaporated 50 nm C60 electron transporting layer and 5 nm BCP as a hole blocking layer on top of the MAPbI3 film. Finally, 100 nm Ag was deposited via high-vacuum thermal evaporation to be an electrode to construct the inverted (p-i-n) perovskite solar cell. All the fabrication procedures (except spin-coating PEDOT:PSS film) were carried out in the nitrogen filled glove box. The area of the cell was defined by a mask which area was measured with the same method we reported.28 The stability of the cell (without sealing) was tested by storing it in the nitrigon filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm, without packing, under continuous illuminating of AM 1.5G, 1 sun (100 mW/cm2) light, the potential of the cell was fixed at 0.95 V (Pmax) and the changes of Jsc and PCE of the cell were recorded every one seconds or under the T5 light illumination at

ca. 500 lux) and measured the efficiency every 5 days. The cell for the stability test in the ambient atmosphere (under ca. 500 lux T5 light illumination and 30% relative humidity at 20 ~ 25oC) was carefully sealed with epoxy resin using the same method we reported previously.36 The large area mini-modules were fabricated basically with the same steps as the small cell except the substrate was enlarge from 1.5 cm x 1.5 cm (containing 4 cells with the dimension of 0.2 cm x 0.5 cm) to 5.0 cm x 5.0 cm (connecting 5 cells in series with the active area of each cell is 0.5 cm x 4.5 cm) with our designed pattern36 using 500 µL of precursor solution, 1 mL anti-solvent (CB) and 1 mL, 1% H2O/CB solution for post treatment. The sun simulator, the I-V and IPCE curves (from the fresh cell without any pre-treatment) measurements, the determination of the photovoltaic parameters as well as the calibration of all measuring facilities are the same as what we reported previously.28 19


ACS Nano 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Acknowledgements Financial support from the Ministry of Science and Technology (MOST), Taiwan, ROC (grand number: NSC104-2113-M-008-002-MY3 and 104-2731-M-008-003MY2) was great acknowledged. The devices fabrication was carried out in Advanced Laboratory of Accommodation and Research for Organic Photovoltaics, MOST, Taiwan, ROC.

Correspondence: Chun-Guey Wu, E-mail: [email protected]

Additional information Supplementary data are collected in the Electronic Supporting Information. This material is available online with the article.

20


Page 20 of 42

Page 21 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

References: (1) Service, R. F. Energy technology. Perovskite Solar Cells Keep on Surging.

Science 2014, 344, 458-458. (2) McGehee, M. D. Materials Science: Fast-track Solar Cells. Nature 2013, 501, 323-325. (3) Zhou, H.; Chen, Q.; Li, G.; Luo, S.; Song, T.; Duan, S.-H.; Hong, Z.; You, J.; Liu, Y.; Yang, Y. Photovoltaics. Interface Engineering of Highly Efficient Perovskite Solar Cells. Science 2014, 345, 542-546. (4) Lee, M. M.; Teuscher, J.; Miyasaka, T.; Murakami, T. N.; Snaith, H. J. Efficient Hybrid Solar Cells based on Meso-superstructured Organometal Halide Perovskites. Science 2012, 338, 643-647. (5) Kazim, S.; Nazeeruddin, M. K.; Grätzel, M.; Ahmad, S. Perovskite as Light Harvester: a Game Changer in Photovoltaics. Angew. Chem. Int. Ed. 2014, 53, 2812-2824. (6) You, J.; Hong, Z.; Yang, Y.; Chen, Q.; Cai, M.; Song, T.-B.; Chen, C.-C.; Lu S.; Liu, Y.; Zhou, H.; Yang, Y. Low-temperature Solution-processed Perovskite Solar Cells with High Efficiency and Flexibility. ACS Nano 2014, 8, 1674-1680. (7) Chiang,

C.-H.;

Tseng,

Z.-L.;

Wu,

C.-G.

Planar

Heterojunction

Perovskite/PC71BM Solar Cells with Enhanced Open-circuit Voltage via a (2/1)-step Spin-coating Process. J. Mater. Chem. A 2014, 2, 15897-15903. (8) Sun, S.; Salim, T.; Mathews, N.; Duchamp, M.; Boothroy, C.; Xing, G.; Sumbc, T. C.; Lam, Y. M. The Origin of High Efficiency in Low-temperature Solution-Processable Bilayer Organometal Halide Hybrid Solar Cells. Energy

Environ. Sci. 2014, 7, 399-407. (9) Eperon, G. E.; Burlakov, V. M.,; Docampo, P.; Goriely, A.; Snaith, H. J. Morphological Control for High Performance, Solution ‐ Processed Planar 21


ACS Nano 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 42

Heterojunction Perovskite Solar Cells. Adv. Funct. Mater. 2014, 24, 151-157. (10) Kojima, A.; Teshima, K.; Shirai, Y.; Miyasaka, T. Organometal Halide Perovskites as Visible-light Sensitizers for Photovoltaic Cells. J. Am. Chem. Soc. 2009, 131, 6050-6051. (11) Docampo, P.; Ball, J. M.; Darwich, M.; Eperon, G. E.; Sniath, H. J. Efficient Organometal Trihalide Perovskite Planar-heterojunction Solar Cells on Flexible Polymer Substrates. Nat. Commun. 2013, 4, 2761-2766. (12) Zuo, C.; Bolink, H. J.; Han, H.; Huang, J.; Cahen, D.; Ding, L. Advances in Perovskite Solar Cells. Adv. Sci. 2016, 3, 1500324. (13) Chiang, C.-H.; Wu, C.-G. Film Grain ‐ Size Related Long ‐ term Stability of Inverted Perovskite Solar Cells. ChemSusChem 2016, 9, 2666-2672. (14) Dong, Q.; Fang, Y.; Shao, Y.; Mulligan, P.; Qiu, J.; Cao, L.; Huang, J. Solar Cells. Electron-hole Diffusion Lengths > 175 µm in Solution-grown CH3NH3PbI3 Single Crystals. Science 2015, 347, 967-970. (15) Nie, W.; Tsai, H.; Asadpour, R.; Blancon, J.-C.; Neukirch, A. J.; Gupta, G.; Crochet, J. J.; Chhowalla, M.; Tretiak, S.; Alam, M. A.; Wang, H.-L.; Mohite, A. D.

High-efficiency

Solution-processed

Perovskite

Solar

Cells

with

Millimeter-scale Grains. Science 2015, 347, 522-525. (16) Burschka, J.; Pellet, N.; Moon, S. J.; Humphry-Baker, R.; Gao, P.; Nazeerruddin, M. K.; Graetze, M. Sequential Deposition as a Route to High-performance Perovskite-sensitized Solar Cells. Nature 2013, 495, 215-219. (17) Chen, Q.; Zhou, H.; Hong, Z.; Luo, S.; Duan, H.-S.; Wang, H.-H.; Liu, Y.; Li, G.;Yang, Y. Planar Heterojunction Perovskite Solar Cells via Vapor-assisted Solution Process. J. Am. Chem. Soc. 2014, 136, 622-625. (18) Chen, C.-W.; Kang, H.-W.; Hsiao, S.-Y.; Yang, P.-F.; Chiang, K.-M.; Lin, H.-W. Efficient and Uniform Planar-type Perovskite Solar Cells by Simple Sequential 22


Page 23 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

Vacuum Deposition. Adv. Mater. 2014, 26, 6647-6652. (19) Jeon, N. J.; Noh, J. H.; Kim, Y. C.; Yang, W. S.; Ryu, S.; Seok, S. l. Solvent Engineering for High-performance Inorganic-organic Hybrid Perovskite Solar Cells. Nat. Mater. 2014, 13, 897-903. (20) Bao, X.; Wang, X, Y.; Zhu, Q.; Wang, N.; Zhu, D.; Wang, J.; Yang, A.; Yang, R. Efficient Planar Perovskite Solar Cells with Large Fill Factor and Excellent Stability. J. Power Sources 2015, 297, 53-58. (21) Ren, Y.-K.; Shi, X.-Q.; Ding, X.-H.; Zhu, J.; Hayat, T.; Alsaedi, A.; Li, Z.-Q.; Xu, X.-X.;.Yang, S.-F.; Dai, S.-Y. Facile Fabrication of Perovskite Layers with Large Grains through a Solvent Exchange Approach. Inorg. Chem. Front. 2018, 5, 348-353. (22) Kim, H. B.; Choi, H.; Jeong, J.; Kim, S.; Walker, B.; Song, S.; Kim, J. Y. Mixed Solvents

for

the

Optimization

of

Morphology

in

Solution-processed,

Inverted-type Perovskite/Fullerene Hybrid Solar Cells. Nanoscale 2014, 6, 6679-6683. (23) Nam, J. J.; Jun, H. N.; Young, C. K.; Woon, S. Y.; Ryu, S.; Seok, S. I. Solvent Engineering for High-performance Inorganic-organic Hybrid Perovskite Solar Cells. Nat. Mater. 2014, 13, 897-903. (24) Lian, J.; Wang, Q.; Yuan, Y.; Shao, Y.; Huang, J. Organic Solvent Vapor Sensitive Methylammonium Lead Trihalide Film Formation for Efficient Hybrid Perovskite Solar Cells. J. Mater. Chem. A 2015, 3, 9146-9151. (25) Ren, Y.-K.; Ding, X.-H.; Wu, Y.-H.; Zhu, J.; Hayat, T.; Alsaedi, A.; Xu, Y.-F.; Li, Z.-Q.; Yang, S.-F.; Dai, S.-Y. Temperature-assisted Rapid Nucleation: a Facile Method to Optimize the Film Morphology for Perovskite Solar Cells. J. Mater.

Chem. A 2017, 5, 20327-20333. (26) Li, W.; Fan, J.; Li, J.; Mai, Y.; Wang, L. Controllable Grain Morphology of 23


ACS Nano 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Perovskite Absorber Film by Molecular Self-assembly toward Efficient Solar Cell Exceeding 17%. J. Am. Chem. Soc. 2015, 137, 10399-10405. (27) Mei, A.; Li, X.; Liu, L.; Ku, Z.; Liu, T.; Rong, Y.; Xu, M.; Hu, M.; Chen, J.; Yang, Y.; Grätzel, M.; Han, H. A Hole-conductor-free, Fully Printable Mesoscopic Perovskite Solar Cell with High Stability. Science 2014, 345, 295-298. (28) Wu, C.-G.; Chiang, C.-H.; Tseng, Z.-L.; Nazeeruddin, K. M.; Hagfeldt, A.; Grätzel, M. High Efficiency Stable Inverted Perovskite Solar Cells without Current Hysteresis. Energy Environ. Sci. 2015, 8, 2725-2733. (29) Eperon, G. E.; Stranks, S. D.; Menelaou, C.; Johnston, M. B.; Herz, L. M.; Snaith, H. J. Formamidinium Lead Trihalide: a Broadly Tunable Perovskite for Efficient Planar Heterojunction Solar Cells. Energy Environ. Sci. 2014, 7, 982-988. (30) Li, X.; Dar, M. I.; Yi, C.; Luo, J.; Tschumi, M.; Zakeeruddin, S. M.; Nazeeruddin, M. K.; Han, H.; Grätzel M. Improved Performance and Stability of Perovskite Solar Cells by Crystal Crosslinking with Alkylphosphonic Acid ω-ammonium Chlorides. Nat. Chem. 2015, 7, 703-711. (31) Heo, J. H.; Song, D. H.; Im, S. H. Planar CH3NH3PbBr3 Hybrid Solar Cells with 10.4% Power Conversion Efficiency, Fabricated by Controlled Crystallization in the Spin‐coating Process. Adv. Mater. 2014, 26, 8179-8183. (32) Liang, P.-W.; Liao, C.-Y.; Chueh, C.-C.; Zuo, F.; Williams, S. T.; Xin, X.-K.; Lin, J.; Jen, A. K.-Y. Additive Enhanced Crystallization of Solution-processed Perovskite for Highly Efficient Planar-heterojunction Solar Cells. Adv. Mater. 2014, 26, 3748-3754. (33) Yang, B.; Dyck, O.; Poplawsky, J.; Keum, J.; Puretzky, A.; Das, S.; Ivanov, I. Perovskite Solar Cells with Near 100% Internal Quantum Efficiency based on 24


Page 24 of 42

Page 25 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

Large Single Crystalline Grains and Vertical Bulk Heterojunctions. J. Am. Chem.

Soc. 2015, 137, 9210-9213. (34) Zuo, C.; Ding, L. An 80.11% FF Record Achieved for Perovskite Solar Cells by Using the NH4Cl Additive. Nanoscale 2014, 6, 9935–9938. (35) You, J.; Yang, Y. (M.); Hong, Z.; Song, T.-B.; Meng, L.; Liu, Y.; Jiang, C.; Zhou, H.; Chang, W.-H.; Li, G.; Yang, Y. Moisture Assisted Perovskite Film Growth for High Performance Solar Cells. Appl. Phys. Lett. 2014, 105, 183902-183906. (36) Chiang, C.-H.; Nazeeruddin, K. M.; Grätzel, M.; Wu, C.-G. The Synergistic Effect of H2O and DMF towards Stable and 20% Efficiency Inverted Perovskite Solar Cell and Module. Energy Environ. Sci. 2017, 10, 808-817. (37) Zhu, W.; Yu, T.; Li, F.; Bao, C.; Gao, H.; Yi, Y.; Yang, J.; Fu, G.; Zhou, X.; Zou,

Z.

A

Facile,

Solvent

Vapor–fumigation-induced,

Self-repair

Recrystallization of CH3NH3PbI3 Films for High-performance Perovskite Solar Cells. Nanoscale 2015, 7, 5427-5434. (38) Yang, M.; Zhang, T.; Schulz, P.; Li, Z.; Li, G.; Kim, D. H.; Guo, N.; Berry, J. J.; Zhu, K.; Zhao, Y. Facile Fabrication of Large-grain CH3NH3PbI3-xBrx Films for High-Efficiency Solar Cells via CH3NH3Br-selective Ostwald Ripening. Nat.

Commun. 2016, 7, 12305. (39) Yang, Z.; Chueh, C.; Zuo, F.; Kim, J. H.; Liang, P. W.; Jen, A. K. Y. High-performance Fully Printable Perovskite Solar Cells via Blade-coating Technique under the Ambient Condition. Adv. Energy Mater. 2015, 5, 1500963-1500984. (40) Sear, R.P. .Nucleation: Theory and Applications to Protein Solutions and Colloidal Suspensions. J. Phys. Condens. Matter. 2007, 19, 033101. (41) Zhou, Y.; Game, O. S.; Pang, S. and Padture, N. P. Microstructures of 25


ACS Nano 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Organometal Trihalide Perovskites for Solar Cells: Their Evolution from Solutions and Characterization. J. Phys. Chem. Lett. 2015, 6, 4827-4839. (42) Hamill, J. C.; Schwartz, J. and Loo, Y. -L. Influence of Solvent Coordination on Hybrid Organic–Inorganic Perovskite Formation. ACS Energy Lett. 2018, 3, 92-97. (43) Bi, C.; Wang, Q.; Shao, Y.; Yuan, Y.; Xiao, Z.; Huang, J. Non-wetting Surface-Driven High-aspect-ratio Crystalline Grain Growth for Efficient Hybrid Perovskite Solar Cells. Nat. Commun. 2015, 6, 7747-7783. (44) Lamer, V. K.; Dinegar, R. H. Theory, Production and Mechanism of Formation of Monodispersed Hydrosols. J. Am. Chem. Soc. 1950, 72, 4847-4854. (45) Ding, B.; Li, Y.; Huang, S.-Y.; Chu, Q.-Q.; Li, C.-X.; Li, C.-J.; Yang, G.-J. Material Nucleation/growth Competition Tuning towards Highly Reproducible Planar Perovskite Solar Cells with Efficiency Exceeding 20%. J. Mater Chem. A 2017, 5, 6840-6848. (46) Yang, M. J.; Zhou, Y. Y.; Zeng, Y. N.; Jiang, C. S.; Padture, N. P.; Zhu, K. Square‐centimeter Solution‐Processed Planar CH3NH3PbI3 Perovskite Solar Cells with Efficiency Exceeding 15%. Adv. Mater. 2015, 27, 6363-6370. (47) Li, X.; Bi, D.; Yi, C.; Décoppet, J.-D.; Luo, J.; Zakeeruddin, S. M.; Hagfeldt, A.; Grätzel, M. A Vacuum Flash-assisted Solution Process for High-efficiency Large-Area pPerovskite Solar Cells. Science 2016, 353, 58-62. (48) Huang, F.; Dkhissi, Y.; Huanga, W.; Xiaoc, M.; Benesperic, I.; Rubanovd, S.; Zhua, Y.; Lina, X.; Jianga, L.; Zhou, Y.; Gray-Weale, A.; Etheridge, J.; McNeill, C.; Caruso, R.; Bach, U.; Spiccia, L.; Cheng, Y. Gas-assisted Preparation of Lead Iodide Perovskite Films Consisting of a Monolayer of Single Crystalline Grains for High Efficiency Planar Solar Cells. Nano Energy 2014, 10, 10-18. (49) Gotanda, T.; Mori, S.; Matsui, A.; Oooka, H. Effects of Gas Blowing Condition 26


Page 26 of 42

Page 27 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

on Formation of Perovskite Layer on Organic Scaffolds. Chem. Lett. 2016, 45, 822-824. (50) Ye, F.; Chen, H.; Xie, F. X.; Tang, W. T.; Yin, M. S.; He, J. J.; Bi, E. B.; Wang, Y. B.; Yang, X. D.; Han, L. Soft-cover Deposition of Scaling-up Uniform Perovskite Thin Films for High Cost-performance Solar Cells. Energy Environ.

Sci. 2016, 9, 2295-2301. (51) Gao, L. L.; Liang, L. S.; Song, X. X.; Ding, B.; Yang, G. J.; Fan, B.; Li, C. X.; Li, C. J. Preparation of Flexible Perovskite Solar Cells by a Gas Pump Drying Method on a Plastic Substrate. J. Mater. Chem. A 2016, 4, 3704-3710. (52) Ding, B.; Gao, L. L.; Liang, Q. Q.; Song, X.; Li, Y.; Yang, G. J.; Fan, B.; Wang, M. K.; Li, C. J.; Li, C. X. Facile and Scalable Fabrication of Highly Efficient Lead Iodide Perovskite Thin-film Solar Cells in Air Using Gas Pump Method.

ACS Appl. Mater. Interfaces 2016, 8, 20068-20074. (53) Ding, B.; Li, Y.; Huang, S.-Y.; Chu, Q.-Q.; Li, C.-X.; Li, C.-J.; Yang, G.-J. Material Nucleation/growth Competition Tuning towards Highly Reproducible Planar Perovskite Solar Cells with Efficiency Exceeding 20%. J. Mater. Chem. A 2017, 5, 6840-6848. (54) Chiang, C.-H.; Chen, C.-C.; Nazeeruddin, K. M.; Wu, C.-G. LiCoO2: A New Hole Transporter for High-efficiency and Thermally Stable Inverted Perovskite Solar Cell. J. Mater. Chem. A, 2018, 6, 13751-13760. (55) Baikie, T.; Fang, Y.; Kadro, J. M.; Schreyer, M.; Wei, F.; Mhaisalkar, S G.; Graetzel, M.; White, T. J. Synthesis and Crystal Chemistry of the Hybrid Perovskite (CH3NH3)PbI3 for Solid-state Sensitised Solar Cell Applications. J.

Mater. Chem. A 2013, 1, 5628-5641. (56) Im, J.-H.; Lee, C.-R.; Lee, J.-W.; Park, S.-W.; Park, N.-G. 6.5% Efficient Perovskite Quantum-dot-sensitized Solar Cell. Nanoscale 2011, 3, 4088-4093. 27


ACS Nano 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 42

(57) Wei, Q.; Mukaida, M.; Naitoh, Y.; Ishida, T. Morphological Change and Mobility Enhancement in PEDOT:PSS by Adding Co-solvents. Adv. Mater. 2013,

5, 2831-2836. (58) Xiao, J. Z.; Bi, C.; Shao, Y.; Dong, Q.; Wang, Q.; Yuan, Y.; Wang, C.; Gao, Y.; Huang, J. Efficient, High Yield Perovskite Photovoltaic Devices Grown by Interdiffusion of Solution-processed Precursor Stacking Layers. Energy Environ.

Sci. 2014, 7, 2619-2623. (59) Xiao, Z.; Dong, Q.; Bi, C.; Shao, Y.; Yuan, Y.; Huang, J. Solvent Annealing of Perovskite-induced

Crystal

Growth

for

Photovoltaic-device

Efficiency

Enhancement. Adv. Mater. 2014, 26, 6503-6509. (60) Frost, J. M.; Butler, K. T.; Brivio, F.; Hendon, C. H.; Schilfgaarde, M. V.; Walsh, A. Atomistic Origins of High-performance in Hybrid Halide Perovskite Solar Cells. Nano Lett. 2014, 14, 2584-2590. (61) Leguy, A. M. A.; Hu, Y.; Campoy-Quiles, M.; Alonso, M. I.; Weber, O. J.; Azarhoosh, P.; Schilfgaarde, M.; Weller, M. T.; Bein, T.; Nelson, J. ; Docampo, P.; Barnes, P. R. F. Reversible Hydration of CH3NH3PbI3 in Films, Single Crystals, and Solar Cells. Chem. Mater. 2015, 27, 3397-3407. (62) Hao, F.; Stoumpos, C. C.; Liu, Z.; Chang, R. P. H.; Kanatzidis, M. G. Controllable Perovskite Crystallization at a Gas–Solid Interface for Hole Conductor-Free Solar Cells with Steady Power Conversion Efficiency over 10%.

J. Am. Chem. Soc. 2014, 136, 16411-16419. (63) Bass, K. K.; McAnally, R. E.; Zhou, S.; Djurovich, P. I.; Thompson, M. E.; Melot, B. C. Influence of Moisture on the Preparation, Crystal Structure, and Photophysical Properties of Organohalide Perovskites. Chem. Commun. 2014, 50, 15819-15822. (64) Gong, X.; Li, M.; Shi, X.-B.; Ma, H.; Wang, Z.-K.; Liao, L.-S. Controllable 28


Page 29 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

Perovskite Crystallization by Water Additive for High‐Performance Solar Cells.

Adv. Funct. Mater. 2015, 25, 6671-6678. (65) Rong, Y.; Hou, X.; Hu, Y.; Mei, A.; Liu, L.; Wang, P.; Han, H. Synergy of Ammonium Chloride and Moisture on Perovskite Cystallization for Efficient Printable Mesoscopic Solar Cells. Nat Commun. 2017, 8, 14555-14562. (66) Green, M. A.; Hishikawa, Y.; Warta, W.; Dunlop, E. D.; Levi, D. H.; Hohl-Ebinger, J.; Ho-Baillie, A. W.Y. Solar Cell Efficiency Tables (version 50).

Prog. Photovolt: Res. Appl. 2017, 25, 668-676. (67) Lin, Q.; Armin, A.; Nagiri, R. C. R.; Burn, P. L.; Meredith, P. Electro-optics of Perovskite Solar Cells. Nat. Photon. 2015, 9, 106-112. (68) Chang, S. H.; Lin, K.-F.; Chang, H.-M.; Chen, C.-C.; Wu, W.-T.; Chen, W.-N.; Wu, P.-J.; Chen, S.-H.; Wu, C.-G. Influence of Organic Cations on High-Performance CH3NH3PbI3 Based Photovoltaics. Sol. Energy Mat. Sol. Cell 2016, 145, 375-381. (69) Saidaminov, M. I.; Abdelhady, A. L.; Murali, B.; Alarousu, E.; Burlakov, V. M.; Peng, W.; Dursun, I.; Wang, L.; He, Y.; Maculan, G.; Goriely, A.; Wu, T.; Mohammed, O. F.; Bakr, O. M. High-quality Bulk Hybrid Perovskite Single Crystals

within Minutes by Inverse Temperature Crystallization. Nat.

Commun. 2015, 6, 7586. (70) Peng, J.; Chen, Y.; Zheng, K.; Pullerits, T.; Liang, Z. Insights into Charge Carrier Dynamics in Organo-metal Halide Perovskites: from Neat Films to Solar Cells. Chem. Soc. Rev. 2017, 46, 5714-5729. (71) Herz, L. M. Charge-Carrier Mobilities in Metal Halide Perovskites: Fundamental Mechanisms and Limits. ACS Energy Lett. 2017, 2, 1539−1548. (72) Wu, C.-G.; Chan, S.-H.; Wang, B.-C. Double ETM for High Efficiency Regular Perovskite Solar Cell. Manuscript in preparation. 29


ACS Nano 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(73) Etgar, L.; Gao, P.; Xue, Z.; Peng, Q.; Chandiran, A. K.; Liu, B.; Nazeeruddin, M. K.; Grätzel, M. Mesoscopic CH3NH3PbI3/TiO2 Heterojunction Solar Cells. J. Am.

Chem. Soc. 2012, 134, 17396-17399. (74) Chang, J.; Zhu, H.; Li, B.; Isikgor, F. H.; Hao, Y.; Xu, Q.; Ouyang, J. Boosting the Performance of Planar Heterojunction Perovskite Solar Cell by Controlling the Precursor Purity of Perovskite Materials. J. Mater. Chem. A 2016, 4, 887-893. (75) Tsai, C.-M.; Wu, G.-W.; Narra, S.; Chang, H.-M.; Mohanta, N.; Wu, H.-P.; Wang, C.-L.; Diau, E. W.-G. Control of Preferred Orientation with Slow Crystallization for Carbon-based Mesoscopic Perovskite Solar Cells Attaining Efficiency 15%. J.

Mater. Chem. A 2017, 5, 739-747.

30


Page 30 of 42

Page 31 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

Figure captions

Figure 1: Schematic representation of the methods used for fabricating MAPbI3 films. Figure 2: SEM images of MAPbI3 films prepared with four different methods. Figure 3: GIWXRD patterns of MAPbI3 films prepared with four different methods Figure 4: SEM images of MAPbI3 films after post treatment with CB containing various amount of H2O. Figure 5: The long-term stability test of the best cell (based ASE/GB-1.0% film) in a glove box. (a) Under continuous illumination of AM 1.5G, 1 sun light (100 mW/cm2).

(b) Stored in the room lighting (T5 lamp, 500 lux at 20 ~ 25oC,

the relative humidity in the glove box and the ambient atmosphere is less than 0.1 ppm and ca. 30%, respectively). Figure 6: I-V curves of the inverted mini-module (connecting 5 cells in series with the active area of each cell of 0.5 cm x 4.5 cm) based on ASE/GB-1.0% film at (a) different scan directions and (b) different scan delay times. Figure 7: Schematic illustration of the function of continuous gas blowing during spin-coating and H2O/CB post treatment. Figure 8: I-V curves of the inverted cell based on FA0.85MA0.15Pb (I0.85Br0.15)3 films prepared with five different methods.

31


ACS Nano 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 42

Table 1: The photovoltaic parameters of the inverted cells based on MAPbI3 films fabricated with assorted methods using various precursor concentrations. a

MAPbI3/DMF

Perovskite

Jsc

Voc

FF

PCE

Concentration

film

(mA/cm2)

(V)

(%)

(%)

SSC

6.20

0.83

36

1.9

1.15 M

b

PCE

(%) 0.88 ± 0.53

1.15 M

8.20 ± CGB

17.7

0.87

66

10 1.37

1.15 M

10.71 ± ASE

19.0

0.93

68

12 0.83

1.15 M

14.29 ± ASE/GB

21.1

0.98

73

15 0.54

1.25 M

15.09 ± ASE/GB-1.25

21.7

1.00

74

16 0.63

1.35 M

16.04 ± ASE/GB-1.35

21.9

1.02

76

17 0.87

1.45 M

12.68 ± ASE/GB-1.45

20.1

1.00

70

14 0.92

a: the maximum value

b: the average value of 10 cells plus standard derivation

32


Page 33 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

Table 2: The photovoltaic parameters, resistances (Series (Rs) and Shunt (Rsh)) of the inverted cells based on ASE/GB-1.35 films before and after post treated with CB containing various amount of H2O a

H2O

Jsc

Voc

FF

content

(mA/cm2)

(V)

(%)

0

21.9

1.02

0.1%

22.6

1.03

d

e

e

23.1

1.06

Rs

Rsh

(%)

(%)

(Ω)

(Ω)

76

17

16.0 ± 0.9

3.39

660

81

19

17.26 ± 0.84

3.51

1790

21

19.5 ± 0.6

1.83

35710

12.40

10.02 ± 1.8

4.75

440

e

PCE

c

PCE

86

1.0%

10%

b

22.8 ± 0.4

1.02 ± 0.02

84 ± 1

20.90

0.86

69

a: In H2O/CB volume ratio. b: The maximum value

c: The average value of 60 cells (except no H2O/CB post treatment).plus standard derivation d: No H2O/CB post treatment. e: Top: the highest value; bottom: the average of 60 cells with standard derivation.

33


ACS Nano 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 42

Table 3: The life-time (τ and τ ) of the two decay paths, the average life-time (τ 1

2

PL

) of

the exciton, the hole mobility and the diffusion length of the perovskite films. Perovskite τ (A )/ns film

1

a

τ (A )/ns

1

2

2

Hole mobility τ

PL

b

Diffusion

/ns cm2/Vs -2

SSC

22.6 (0.20)

2.22 (0.80)

16.81

2.39*10

ASE

24.2 (0.37)

2.90 (0.63)

20.55

2.83*10

CGB

22.8 (0.78)

3.14 (0.22)

22.09

3.31*10

ASE/GB

----

37.50 (1.0)

37.50

3.57*10

ASE/GB-1.0%

----

120.2 (1.0)

120.2

5.79*10

-2

-2

-2

-2

length (nm) 32 35 44 59 134

a: the average lifetime (τ ) was calculated with the statistical definition reported by Tsai76 et al. PL

b: the diffusion length was calculated by combining the carrier life-time with the hole mobility using the equation proposed by Bakr70 et al.

34


Page 35 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

Figure 1

35


ACS Nano 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 2

36


Page 36 of 42

Page 37 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

Figure 3

37


ACS Nano 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 4

38


Page 38 of 42

Page 39 of 42

Figure 5

PCE/initial PCE

1.0

(b) 0.8 0.6 0.4

in glove box in ambient atmosphere 0.2 0

5

10

15

20

25

30

Time (day)

1.0

PCE/initial PCE

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

(b) 0.8 0.6 0.4

in glove box in ambient atmosphere 0.2 0

5

10

15

20

25

30

Time (day)

39


ACS Nano

Current density (mA/cm2)

Figure 6

(a)

4 2 0 -2

Scan from negtive to positive bias Scan from positive to negative bias

-4 0

Current density (mA/cm2)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 40 of 42

1

2

3

Voltage (V)

4

5

(b)

4 2 0

0 ms 100 ms 200 ms 500 ms

-2 -4 0

1

2

3

Voltage (V)

4

40


5

Page 41 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

Figure 7

41


ACS Nano

Figure 8

Current Density (mA/cm2)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 42 of 42

25 20 15

SSC CGB ASE ASE/GB ASE/GB-1.0%

10 5 0 -5 -10 -15 0.0

0.2

0.4

0.6

0.8

1.0

Voltage (V)

42


A Method for the Preparation of Highly Oriented MAPbI3 Crystallites

Recommend Documents