Novel Low-Temperature Process for Perovskite Solar Cells with a

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Novel Low-Temperature Process for Perovskite Solar Cells with a Mesoporous TiO2 Scaffold Patricia Samia Cerian Schulze, Alexander J. Bett, Kristina Winkler, Andreas Hinsch, Seunghun Lee, Simone Mastroianni, Laura E. Mundt, Markus Mundus, Uli Würfel, Stefan Glunz, Martin Hermle, and Jan Christoph Goldschmidt ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b05718 • Publication Date (Web): 23 Aug 2017 Downloaded from http://pubs.acs.org on August 24, 2017

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ACS Applied Materials & Interfaces

Novel Low-Temperature Process for Perovskite Solar Cells with a Mesoporous TiO2 Scaffold Patricia S.C. Schulze*,†,║, Alexander J. Bett†,║, Kristina Winkler†, Andreas Hinsch†, Seunghun Lee†,┴, Simone Mastroianni†,‡, Laura E. Mundt†, Markus Mundus†, Uli Würfel†,‡, Stefan W. Glunz†,§, Martin Hermle†, and Jan Christoph Goldschmidt† †

Fraunhofer Institute for Solar Energy Systems, Heidenhofstraße 2, 79110 Freiburg, Germany

‡

Freiburg Materials Research Center (FMF), Albert-Ludwigs-University of Freiburg, Stefan-

Meier-Straße 21, 79104 Freiburg, Germany §

Freiburg Center for Interactive Materials and Bioinspired Technologies (FIT), Albert-Ludwigs-

University of Freiburg, Georges-Köhler-Allee 105, 79110 Freiburg, Germany KEYWORDS: perovskite solar cell, low-temperature process, titanium dioxide scaffold, titanium dioxide evaporation, perovskite silicon tandem solar cell

ABSTRACT The most efficient organic-inorganic perovskite solar cells (PSCs) contain the conventional n-i-p mesoscopic device architecture using a semiconducting TiO2 scaffold combined with a compact TiO2 blocking layer for selective electron transport. These devices achieve high power conversion efficiencies (15% to 22%), but mainly require high-temperature

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sintering (>450 °C), which is not possible for temperature-sensitive substrates. So far, comparably little effort has been spent on alternative low-temperature (200 °C.21,23 Furthermore, we also observed performance degradation at temperatures above 300 °C for other solar cell technologies, when combined with an indium tin oxide (ITO) layer, which is also an appropriate interconnection material between the two sub-cells in tandem devices (see also Figure S1 in the Supporting Information (SI)).24 To overcome this limitation, several deposition techniques for the compact TiO2 (c-TiO2) layer that are compatible with temperature-sensitive substrates, were successfully implemented in PSCs, such as spin-coating,25–27 atomic layer deposition (ALD),28–30 sputtering,31–33 as well as electron beam evaporation.34,35 Alternative low-temperature (low-T) processes for the mesoporous TiO2 scaffold like low-T sintering of sol-gel TiO2 particles,36 compression,37 or UV irradiation treatments38 are known from the development of DSSCs on flexible substrates. Contradicting peer-reviewed publications stating that TiO2-based mp-structured PSCs cannot be realized at low temperatures,39–41 a proofof-principle on flexible substrates was presented by Di Giacomo et al. in 2015.42 Flexible cells with low-temperature plasma-assisted ALD for the TiO2 compact layer and a UV treatment for the TiO2 scaffold reached an average power conversion efficiency (PCE) of 7.1%. Recently, they presented low-temperature perovskite solar cells on glass substrates with PCEs of up to 15.9%.43 In this work, we investigate low-temperature fabrication routes (99%, Sigma-Aldrich). Patterned substrates were cleaned in an ultrasonic bath using first detergent (Mucasol, Schülke & Mayr) in deionized water and then ethanol for 15 min each. The TiO2 compact layer was deposited by electron beam evaporation in an evaporation tool (Pfeiffer PLS 570) equipped with a voltage electron gun (Telemark Model 267) with a rate of 1 nm s-1 controlled by an oscillating crystal. The temperature and the pressure in the chamber were approximately 20 °C and 10-4 mbar, respectively, during the process. For comparison a high-temperature process via spray pyrolysis deposition (at 470 °C) was carried out using a titanium diisopropaxide bis(acetylacetatonate) solution (75 wt. % in isopropanol, Aldrich Chemistry) diluted in ethanol (volume ratio 1:39). The mesoporous TiO2 scaffold was


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deposited by spin-coating (2500 rpm for 10 s, 7000 rpm for 40 s) a commercial paste (Dyesol 18NR-T) diluted with ethanol (99.5%, Carl Roth) and anhydrous terpineol (65% α, 10% β, 20% γ, Sigma-Aldrich) in a mass ratio of 1:2:4. All low-temperature devices were exposed to UV irradiation in a UV chamber (UVACUBE 100, Hönle) equipped with an Iron lamp for up to 200 min in ambient atmosphere. High-temperature devices were sintered on a closed hotplate applying a temperature profile of up to 525 °C. For the perovskite precursor solution, 0.25 g ml-1 methylammonium iodide (Dyesol) and 0.7225 g ml-1 lead (II) iodide (TCI) were dissolved in 1 ml of anhydrous dimethyl sulfoxide (≥99.9%, Sigma-Aldrich) and stirred at 60 °C overnight. 100 µl of warm precursor solution were spin-coated onto substrates (1000 rpm for 10 s, 5000 rpm for 20 s) adding 200 µl toluene (≥99.5%, Carl Roth) as anti-solvent 5 s prior to the end of spinning. Substrates were annealed at 100 °C for 60 min. For the hole-transporting material (HTM) a doped Spiro-OMeTAD formulation was prepared according to Burschka et al.17 and deposited by spin-coating (500 rpm for 1 s, 4000 rpm for 30 s). For the champion device built after further process adaption, 56 mg (2,2′,7,7′-tetrakis(N,Ndi-p-methoxyphenylamine)-9,9-spirobifluorene) (Spiro-OMeTAD) (99%, Sigma-Aldrich) in 650 µl chlorobenzene (stirred for 30 min at 70 °C), 14 µl of a stock solution of 6.25 g ml−1 bis(trifluormethane)sulfonamide lithium salt (Sigma-Aldrich) in acetonitrile and 20 µl 4-tertbutylpyridine (96%, Sigma-Aldrich) were mixed and kept 3 h prior to spin-coating. Gold electrodes were deposited by thermal evaporation (100 nm) under high vacuum (10-6 mbar). An evaporation mask defined three cells on each substrate. Perovskite, HTM, and gold contact deposition were carried out in nitrogen atmosphere.


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2.2 Characterization IV: Current-Voltage (IV) characteristics were measured using a solar simulator provided with a 1000 W xenon short arc lamp and a source meter (Keithley 2651A). Light intensity was calibrated using a silicon reference solar cell in order to have 1 sun intensity (AM 1.5 global spectrum). First, the reverse scan direction was measured (1.2 V to -0.1 V) followed by the forward scan direction (-0.1 V to 1.2 V). If not mentioned otherwise in the text, the scan speed was 43 mV s-1. A black shadow mask defined an active area of 0.16 cm² during measurement. All IV measurements were carried out in air. For stabilized efficiency measurements, a LED solar sun simulator (WAVELABS, SINUS-220) was used. The light intensity was calibrated with the same silicon reference solar cell (1 sun instensity, AM 1.5 global spectrum). The voltage of the maximum power point (VMPP) was determined from IV scans both in reverse and forward direction. The mean VMPP was then applied for 90 s tracking the efficiency. EQE: The external quantum efficiency (EQE) measurement was performed with a laser-based EQE setup developed in-house.44 The monochromatic radiation from the laser system has been chopped at 70 Hz and illuminated an area significantly larger than the active cell area. A shadow mask of 0.16 cm2 area was used for defining the measured cell area. The setup has been calibrated by a reference measurement using a Silicon World Photovoltaic Scale (WPVS) reference solar cell. The cell temperature was approximately 25 °C without active temperature control. Bias light from multiple LEDs emitting at 450 nm was used to generate a cell bias current of approximately 0.4 mA. PL/ LBIC: photoluminescence (PL) and light beam induced current (LBIC) maps were obtained within one measurement using a photoluminescence spectroscopy setup, based on a


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confocal microscope.45 By spot-wise illumination and detection through the same lens and an appropriate pinhole, the detection volume can be controlled and minimized, allowing for a very high spatial resolution by scanning the sample. A frequency doubled Nd:YAG laser (532 nm) with a photon flux of 3.41×1018 photons s-1 cm-2 was used. As the samples are illuminated from the glass side, the reflected excitation light as well as the emitted PL will be detected in this reflection mode. In order to suppress spurious reflected laser light, a cold-light beam splitter as well as an additional long pass filter was applied in the beam path. For detection of the PL signal, a silicon line CCD combined with a grating spectrometer was used. By scanning the sample using a movable x-y stage, the PL spectrum was obtained for every measurement spot. The analysis of the PL peak allows for the determination of the peak height as well as the spectral peak position for each spot. Simultaneously the current, induced by the spot-wise laser excitation, was measured after amplification by a low-noise preamplifier. SEM/ EDX: The investigation of the surface and cross section of TiO2 and TiO2/perovskite films, as well as of complete devices was carried out through a Schottky emission scanning electron microscope (SEM, Zeiss, Auriga 60) at 5 kV. Quantitative elemental analysis was determined from energy dispersive X-ray (EDX) spectra acquired with a Silicon drift detector (Bruker, XFlash 6/60) at 7 kV. 3. RESULTS 3.1. Low-Temperature Fabrication Route We developed the process sequence shown in Figure 1a that allows for a complete lowtemperature fabrication of PSCs with the common FTO/c-TiO2/mp-TiO2/Perovskite/SpiroOMeTAD/Au configuration. Herein, vacuum electron beam evaporation is used to deposit a


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20 nm thick c-TiO2 layer. Substrates are kept at room temperature during the process. The layer thickness was chosen after an initial thickness optimization test of 10 nm, 20 nm, 30 nm, and 50 nm. Solar cells with a 20 nm thick evaporated c-TiO2 layer showed the highest efficiencies due to superior average short-circuit current density (JSC) and open-circuit voltage (VOC). In the following step, a TiO2 nanoparticle paste was spin-coated onto the substrate and subsequently exposed to UV irradiation under ambient atmosphere. Conventionally high-T sintering is applied to form an mp-TiO2 scaffold layer with a clean and highly crystalline surface for efficient electron transport. By replacing sintering with a low-T UV treatment, the photoactivity of TiO2 under UV light exposure is used to decompose organic compounds such as the cellulose binders of the TiO2 paste. After 120 min of UV curing, an effective removal of organics is achieved, apparent from the layer’s carbon content determined by energy dispersive X-ray spectroscopy (EDX) (Figure S2). Furthermore, the UV curing process was tested on silicon heterojunction solar cell precursors, which could serve as bottom solar cells in a perovskite silicon tandem device. No significant change in the implied VOC or the implied FF was observed both in quasi steady-state photoconductance (QSSPC) and SunsVOC measurements. Details concerning the investigated silicon samples can be found in the SI (see Figure S3). For comparison, solar cells were also fabricated by a conventional high-temperature process. In this case, the compact TiO2 layer was deposited by spray pyrolysis at 470 °C and substrates were sintered at 525 °C after spin-coating the TiO2 paste for the mesoporous scaffold. More details about materials and process steps are given in the experimental section. Figure 1b shows a sketch of the whole layer stack. A photograph of a substrate taken from the gold contact side can be seen in Figure 1c highlighting the active area. Figure 1d shows a scanning electron microscope (SEM) image of a low-T perovskite solar cell in its cross section. It is clearly visible


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that the evaporation of TiO2 allows for conformal coating on the rough FTO surface (+/-100 nm) and formation of a closed c-TiO2 blocking layer.

Figure 1. a) Process sequences for perovskite solar cell fabrication with high- and lowtemperature process. b) Sketch of a perovskite solar cell considered in this work. c) Photograph of a substrate containing three cells from the gold contact side. The three active areas of each 0.16 cm² are colored in yellow. d) Scanning electron microscope (SEM) picture of a perovskite solar cell fabricated by the low-temperature process. 3.2. Low-Temperature Perovskite Solar Cells


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Different periods of time ranging from 0 to 200 min of UV treatment for the mp-TiO2 layer were applied to investigate its effect on perovskite formation and device performance. Figure 2 shows a series of photographs and SEM images after the perovskite deposition for all periods of UV light exposure time. When depositing the perovskite precursor solution, a difference in substrate wetting behavior can be observed; on substrates without UV treatment the precursor solution forms droplets with a high contact angle, whereas a liquid film is obtained with increasing duration of UV light exposure. Consequently, most of the precursor is removed during the spin-coating process for samples not treated with UV light, resulting in poor deposition of perovskite absorber after annealing. After 40 min of UV curing a higher extent of perovskite crystals is formed, but numerous voids are still present. For a UV curing time of 80 min the perovskite layer on the photograph looks closed, but the SEM image still reveals pinholes in the µm-range. These vanish for longer UV curing times. A closed perovskite layer comparable to the high-T process was obtained for UV treatments of at least 120 min.

Figure 2. Influence of mesoporous TiO2 treatment on perovskite formation. a) Photographs of the samples after the perovskite formation. b) Corresponding SEM images. The black scale bar is 500 µm. For better visualization the right part of the SEM images is colored, perovskite in


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orange and underlying TiO2 in blue. To form a closed perovskite layer a UV curing time of at least 120 min is needed. Figure 3 shows the solar cell parameters (short-circuit current density JSC, open-circuit voltage VOC, fill factor FF, and efficiency) of low-temperature processed cells for the range of applied UV curing times. The current-voltage (IV) characteristics of the cells were measured first in reverse and then in the forward scan direction from 1.2 V to -0.1 V under 1 sun illumination using a shadow mask defining cell areas of 0.16 cm² each. As without UV treatment no proper perovskite layer was formed, no cells were manufactured with a UV curing time of 0 min. For 40 min and 80 min UV treatment the performance is very poor. The only partially formed perovskite layer results in a low JSC considerably below 10 mA cm-2, and a poor fill factor yielding efficiencies of below 4%. However, with a longer UV curing time of 120 min the performance increases significantly and further improves for 160 min. By extending the UV curing time to 200 min further improvement in average cell performance can be noticed with a decreasing spread for JSC and VOC. These cells reach short-circuit current densities of around 20 mA cm-2 and open-circuit voltages of around 1 V. The fill factor is in the range between 60% to 70% and 70% to 80% for the forward and reverse scan direction, respectively. This leads to efficiencies of up to 14.3% and 16.0% for the forward and reverse scan direction, respectively. With increasing UV curing time, not only does the efficiency improve but the hysteresis decreases also (Figure S4 and Figure S5). More details on the IV measurements can be found in the SI.


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Figure 3. a) Short-circuit current density (JSC), b) open-circuit voltage (VOC), c) fill factor (FF) and d) efficiency of perovskite solar cells manufactured using the low-temperature process as a function of UV curing time. For each curing time, data from forward (for) and reverse (rev) scan direction are shown. 50% of the data points are within the boxes, 80% within the whiskers. The horizontal line and the point in the boxes represent the median and the mean value, respectively. Effectively operating solar cells can only be obtained after at least 120 min of UV curing. The performance improves further for longer UV curing times.


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Figure 4 shows the normalized external quantum efficiency (EQE) of a solar cell that has undergone an UV treatment for 200 min measured at 70 Hz chopping frequency and approximately 0.12 suns bias irradiance from LEDs emitting at 450 nm. An EQE measurement at 400 nm was recorded before and after the EQE scan. During the measurement duration of 14 min under short-circuit conditions the cell’s EQE at 400 nm decreased by 4.7%rel. As the measurement was conducted from longer to shorter wavelengths (indicated by the arrow) shorter wavelengths might be subject to increasing underestimation. This effect is discussed in more detail in the SI (Figure S6).

Figure 4. External quantum efficiency (EQE) of a perovskite solar cell fabricated by the low-T process with 200 min of UV curing normalized to the maximum value. Chopping frequency was 70 Hz. The arrow indicates the wavelength scan direction. In order to gain insight into the lateral performance distribution and ETM layer quality, spatially resolved photoluminescence spectroscopy (PLS) and light beam induced current (LBIC) measurements were performed on selected cells, using an excitation wavelength of 532 nm. A description of the measurement setup can be found in the experimental section as well as a detailed introduction in literature46,47. In Figure 5, the results for two cells with 120 min and


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200 min of UV treatment, respectively, are depicted: the current distribution (a), the height (b) as well as the spectral peak position (c) of the Gaussian distribution that has been fitted to the PL spectrum. In accordance with the obtained IV data, the overall current is higher for the cell which experienced the extended UV curing time. Also the current is more evenly distributed compared to the cell with shorter UV curing time. The PL intensity exhibits a different trend: even though the overall cell performance is lower, the PL intensity is higher for the cell with shorter UV curing time. For both cells the PL peak is located around 772 nm, which is characteristic for the applied perovskite absorber MAPbI3. However, the PL-peaks are slightly broadened towards longer wavelengths, resulting also into a small red-shift of the PL-peak (see Figure5d) in regions where some distortions of the homogenous layers can be observed (circles in Figure 5c). The origin of this red-shift is currently unknown.

Figure 5. a) Light beam induced current (LBIC), b) intensity and c) spectral position of the photoluminescence (PL) peak for two samples with different UV curing periods of the


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mesoporous TiO2 layer. d) PL spectra corresponding to the positions marked with circles in b) and c). With increasing UV curing time, the current increases but the PL intensity decreases. This anticorrelation can be attributed to a better contact between perovskite and TiO2 electron contact in case of the longer UV treatment. 3.3. Comparison of High- and Low-Temperature Processed PSCs Figure 6 shows a comparison of solar cell results between the common high-T (spray pyrolysis and sintering) and the low-T process investigated in this work (evaporation and UV curing). In Figure 6a and Figure 6b the IV curves of the best cells with high-temperature and lowtemperature TiO2, respectively, are shown. The inset tables show the related values of JSC, VOC, FF and efficiency. Figure 6c represents a comparison between the best high-T and the best low-T batch concerning solar cell parameters. The corresponding values are listed in the SI in Table S1. The difference in FF and JSC between data obtained from forward and reverse scan direction is slightly more pronounced for low-T cells. Nevertheless, low-T processed cells achieve an average efficiency value only 0.5% lower than the high-T route, underlining that both processes reach comparably good results.


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Figure 6. IV curves of the best solar cells produced by the a) high-temperature and b) lowtemperature process. Scan rate was 43 mV s-1. c) Comparison of JSC, VOC, FF and efficiency ɳ of solar cell batches manufactured by high- and low-temperature process. 50% of the data points are within the boxes, 80% within the whiskers. The horizontal line and the point in the boxes represent the median and the mean value, respectively. Solar cell results are comparable for both processes. The inset photographs were taken after perovskite deposition and show that a closed perovskite layer is formed for both processes. 3.4. Further Process Adaption After further process optimization and slightly adjusting the Spiro-OMeTAD formulation, our low-T processed cells improved in performance. In the following, latest results of our low-T record cell are presented. Figure 7a and Figure 7b show the IV curve and the stabilized


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efficiency of 18.2% operating under VMPP, respectively. The inset table shows the related values of JSC, VOC, FF and efficiency. A histogram of the efficiency values achieve for the whole batch (15 cells) can be found in the SI (Figure S7), showing the relative small spread and good reproducibility.

Figure 7. a) IV curve of the best solar cell produced by the low-temperature process with adjusted Spiro-OMeTAD formulation. Scan rate was 19 mV s-1. b) Stabilized efficiency measurement keeping the cell at VMPP. The horizontal red line shows a stabilized efficiency of 18.2%. 4. DISCUSSION As shown in Figure 2, a longer UV curing time produces a significantly improved perovskite layer formation. This correlates with a reduction of carbon content (Figure S2), which can be associated with a removal of the organic binders. The two results together underline that organic binders have to be effectively removed for good wetting of the perovskite precursor solution and for the infiltration of the mesoporous scaffold to form a pinhole-free capping layer. Furthermore, longer curing times correlate with reduced hysteresis (Figure S4) and high currents in the IV scan (Figure 3a) and LBIC measurements (Figure 5a), respectively. Interestingly, the PL


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intensity shows an opposite trend. Here a cell with a UV curing time of 120 min has a higher intensity than a cell treated for 200 min. Both observations, however, are convincingly explained by the hypothesis that the removal of the non-conductive organic binders is necessary for effective electron extraction by the TiO2. At shorter curing times, this removal is incomplete and electrons get extracted insufficiently into the TiO2 conducting band; hence the radiative recombination of charge carriers within the perovskite layer is elevated. This anti-correlation between PL intensity and LBIC has already been observed by Eperon et al.48 for high-T PSCs (320 °C) with p-i-n device architecture. Furthermore, the established connection between electron contact quality and overall performance/ hysteresis is in accordance to investigations of improving electron contact quality using doping,49 different deposition techniques50 and double electron extraction layers51 for improved charge extraction. In addition, the spatially resolved techniques revealed that agglomerates of TiO2 nanoparticles or external contamination like dust attached to the surface can cause inhomogeneous deposition of subsequent layers. Spin-coating the perovskite precursor solution can be particularly affected, resulting in comet-like features influencing both the perovskite’s PL intensity and peak position.52 Moreover, stripes arising from a pipette tip used for spreading solution before spincoating can be identified. Interestingly, cells featuring inhomogeneity could still reach reasonable efficiencies, underlining that the cells are most likely contact limited. However, there is still room for process optimization. Comparing our entirely low-T and the conventional high-T process routes, TiO2-scaffolded PSCs achieved similar performances, which underlines the applicability of our fabrication route. Furthermore, our entirely low-temperature processed PSCs exceed the performance recently presented representing the most efficient low-T mesoporous PSCs up to now.43 In this case ALD


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was used for the compact layer and a UV treatment for the mp-TiO2. The reverse scan efficiency of their best cell was 15.9%. Our latest results with adjusted Spiro-OMeTAD formulation clearly exceed this value (18.1% forward scan, 19.1% reverse scan), while the slight hysteresis behavior for the low-T cells is similar. Additionally to the IV scans, we present the stabilized efficiency measurement under operating conditions reaching a value of 18.2%. Please note that this stabilized value is closer to the result of the forward IV-scan, as the reverse direction shows a hump around maximum power point, leading to an overestimation of FF and efficiency. Possible reasons might be charge accumulation and ion migration. Concerning the two different deposition techniques applied for low-T c-TiO2 layers, evaporation used in this work is more attractive than ALD in terms of reduced process complexity and deposition duration. So far, our low-T PSCs represent the first mp-structured PSCs with an evaporated TiO2 blocking layer. Our results reveal that vacuum deposition provides high-quality TiO2 thin films that can directly attach even to rough FTO surfaces (Figure 1d and Figure S2). Furthermore, the selective transport of electrons was affirmed by the high efficiency values measured. 5. CONCLUSION We demonstrated that low-temperature perovskite solar cells with an evaporated compact TiO2 layer and a UV cured mesoporous TiO2 scaffold represent a viable route for efficient cell fabrication. Vacuum evaporation was introduced as a convenient deposition technique of uniform c-TiO2 layers for mp-structured PSCs, adapting smoothly to the rough FTO substrate surface, and being less complex compared to other low-T techniques like ALD. In addition,


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effective removal of organic binders for the mp-TiO2 by UV light replacing high-T sintering was presented. The best cell reached a stabilized efficiency of 18.2% under operating conditions. Increasing the UV curing time (from 0 to 200 min) results in an increase of all solar cell parameters (JSC, VOC, FF) and a decrease of hysteresis due to the improved mp-TiO2 wettability and thus improved perovskite/TiO2 contact quality. The low-temperature cells produced in this work are comparable to cells produced by a conventional high-temperature route (spray pyrolysis deposition of the cTiO2 and sintering of the mp-TiO2 scaffold). The obtained results highlight the general applicability of the classical TiO2-based mesoporous device architecture for temperaturesensitive substrates, like high-efficiency silicon heterojunction solar cells or other silicon bottom cells with ITO interconnection layer for tandem devices, without forfeiting efficiency. ASSOCIATED CONTENT Supporting Information Incompatibility of high temperatures for silicon solar cells with indium tin oxide as front layer; SEM images and corresponding EDX analysis approving effective removal of organic binders by UV treatment to form the mesoporous TiO2 scaffold; UV curing of silicon heterojunction precursors; hysteresis effect analysis for all solar cells presented; current-voltage curves for all UV curing times and high-temperature; solar cell performance parameters for all UV curing times and high-temperature; investigation of performance decrease during EQE measurement and measurement repetition after preconditioning; efficiency histogram of the batch of the record cell (PDF)


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AUTHOR INFORMATION Corresponding Author *

P.S.C. Schulze. E-mail: [email protected]

Present Addresses ┴

S. Lee: Korea University, Anam Campus, Anam-dong 5-ga, Seongbuk-gu, Seoul, Korea

Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. ║P.S.C. Schulze and A.J. Bett contributed equally to this work. Funding Sources This work was partially funded by the Bundesministerium für Wirtschaft und Energie (German Federal Ministry for Economic Affairs and Energy) under contract number 0324037A (Perowskit-Silizium Tandemsolarzellen – PersiST). A.J. Bett gratefully acknowledges scholarship support from the Deutsche Bundesstiftung Umwelt (DBU). ACKNOWLEDGMENT The authors would like to thank H. Steidl, J. Zielonka and R. Sharma for their support with processing and measurement and M. Bivour for providing silicon heterojunction precursors. REFERENCES (1) 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.


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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


(2) NREL. Best Research-Cell Efficiencies. http://www.nrel.gov/ncpv/images/efficiency_chart.jpg (accessed February 9, 2017). (3) Zhou, Z.; Pang, S.; Liu, Z.; Xu, H.; Cui, G. Interface Engineering for High-Performance Perovskite Hybrid Solar Cells. J. Mater. Chem. A 2015, 3, 19205–19217. (4) Salim, T.; Sun, S.; Abe, Y.; Krishna, A.; Grimsdale, A. C.; Lam, Y. M. Perovskite-Based Solar Cells: Impact of Morphology and Device Architecture on Device Performance. J. Mater. Chem. A 2015, 3, 8943–8969. (5) Heo, J. H.; Han, H. J.; Kim, D.; Ahn, T. K.; Im, S. H. Hysteresis-Less Inverted CH3NH3PbI3 Planar Perovskite Hybrid Solar Cells with 18.1% Power Conversion Efficiency. Energ. Environ. Sci. 2015, 8, 1602–1608. (6) Zhang, W.; Saliba, M.; Moore, D. T.; Pathak, S. K.; Horantner, M. T.; Stergiopoulos, T.; Stranks, S. D.; Eperon, G. E.; Alexander-Webber, J. A.; Abate, A.; Sadhanala, A.; Yao, S.; Chen, Y.; Friend, R.H.; Estroff, L.A.; Wiesner, U.; Snaith, H.J. Ultrasmooth Organic-Inorganic Perovskite Thin-Film Formation and Crystallization for Efficient Planar Heterojunction Solar Cells. Nat. Commun. 2015, 6, 6142. (7) Leijtens, T.; Eperon, G. E.; Pathak, S.; Abate, A.; Lee, M. M.; Snaith, H. J. Overcoming Ultraviolet Light Instability of Sensitized TiO2 with Meso-Superstructured Organometal TriHalide Perovskite Solar Cells. Nat. Commun. 2013, 4, 2885. (8) Ball, J. M.; Lee, M. M.; Hey, A.; Snaith, H. J. Low-Temperature Processed MesoSuperstructured to Thin-Film Perovskite Solar Cells. Energ. Environ. Sci. 2013, 6, 1739.


23


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 24 of 31

(9) Liu, D.; Yang, J.; Kelly, T. L. Compact Layer Free Perovskite Solar Cells with 13.5% Efficiency. J. Am. Chem. Soc. 2014, 136, 17116–17122. (10) Shi, J.; Dong, J.; Lv, S.; Xu, Y.; Zhu, L.; Xiao, J.; Xu, X.; Wu, H.; Li, D.; Luo, Y.; Meng, Q. Hole-Conductor-Free Perovskite Organic Lead Iodide Heterojunction Thin-Film Solar Cells: High Efficiency and Junction Property. Appl. Phys. Lett. 2014, 104, 63901. (11) Zhao, Y.; Zhu, K. Organic-Inorganic Hybrid Lead Halide Perovskites for Optoelectronic and Electronic Applications. Chem. Soc. Rev. 2016, 45, 655–689. (12) Zhou, H.; Chen, Q.; Li, G.; Luo, S.; Song, T.-B.; Duan, H.-S.; Hong, Z.; You, J.; Liu, Y.; Yang, Y. Interface Engineering of Highly Efficient Perovskite Solar Cells. Science 2014, 345, 542–546. (13) Gao, X.-X.; Ge, Q.-Q.; Xue, D.-J.; Ding, J.; Ma, J.-Y.; Chen, Y.-X.; Zhang, B.; Feng, Y.; Wan, L.-J.; Hu, J.-S. Tuning the Fermi-Level of TiO2 Mesoporous Layer by Lanthanum Doping Towards Efficient Perovskite Solar Cells. Nanoscale 2016, 8, 16881–16885. (14) Zhang, H.; Shi, J.; Xu, X.; Zhu, L.; Luo, Y.; Li, D.; Meng, Q. Mg-Doped TiO2 Boosts the Efficiency of Planar Perovskite Solar Cells to Exceed 19%. J. Mat. Chem. A 2016, 4, 15383– 15389. (15) Giordano, F.; Abate, A.; Correa Baena, J. P.; Saliba, M.; Matsui, T.; Im, S. H.; Zakeeruddin, S. M.; Nazeeruddin, M. K.; Hagfeldt, A.; Graetzel, M. Enhanced Electronic Properties in Mesoporous TiO2 via Lithium Doping for High-Efficiency Perovskite Solar Cells. Nat. Commun. 2016, 7, 10379.


24

Page 25 of 31

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


(16) Ito, S.; Tanaka, S.; Manabe, K.; Nishino, H. Effects of Surface Blocking Layer of Sb2S3 on Nanocrystalline TiO2 for CH3NH3PbI3 Perovskite Solar Cells. J. Phys. Chem. C 2014, 118, 16995–17000. (17) Burschka, J.; Pellet, N.; Moon, S.-J.; Humphry-Baker, R.; Gao, P.; Nazeeruddin, M. K.; Grätzel, M. Sequential Deposition as a Route to High-Performance Perovskite-Sensitized Solar Cells. Nature 2013, 499, 316–319. (18) Yang, W. S.; Noh, J. H.; Jeon, N. J.; Kim, Y. C.; Ryu, S.; Seo, J.; Seok, S. I. HighPerformance Photovoltaic Perovskite Layers Fabricated through Intramolecular Exchange. Science 2015, 348, 1234–1237. (19) Werner, J.; Walter, A.; Rucavado, E.; Moon, S.-J.; Sacchetto, D.; Rienaecker, M.; Peibst, R.; Brendel, R.; Niquille, X.; De Wolf, S.; Löper. P.; Morales-Masis, M.; Nicolay, S.; Niesen, B.; Ballif, C. Zinc Tin Oxide as High-Temperature Stable Recombination Layer for Mesoscopic Perovskite/Silicon Monolithic Tandem Solar Cells. Appl. Phys. Lett. 2016, 109, 233902. (20) Wolf, S. de; Descoeudres, A.; Holman, Z. C.; Ballif, C. High-efficiency Silicon Heterojunction Solar Cells: A Review. Green 2012, 2, 7–24. (21) Masuko, K.; Shigematsu, M.; Hashiguchi, T.; Fujishima, D.; Kai, M.; Yoshimura, N.; Yamaguchi, T.; Ichihashi, Y.; Mishima, T.; Matsubara, N. Yamanishi, T.; Takahama, T.; Taguchi, M.; Maruyama, E.; Okamoto, S. Achievement of More Than 25% Conversion Efficiency with Crystalline Silicon Heterojunction Solar Cell. IEEE J. Photovolt. 2014, 4, 1433– 1435.


25


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 26 of 31

(22) Yoshikawa, K.; Kawasaki, H.; Yoshida, W.; Irie, T.; Konishi, K.; Nakano, K.; Uto, T.; Adachi, D.; Kanematsu, M.; Uzu, H.; Yamamoto, K. Silicon Heterojunction Solar Cell with Interdigitated Back Contacts for a Photoconversion Efficiency over 26%. Nat. Energ. 2017, 2, 17032. (23) Wolf, S. de; Kondo, M. Nature of Doped a-Si: H/c-Si Interface Recombination. J. Appl. Phys. 2009, 105, 103707. (24) Albrecht, S.; Saliba, M.; Correa Baena, J. P.; Lang, F.; Kegelmann, L.; Mews, M.; Steier, L.; Abate, A.; Rappich, J.; Korte, L.; Schlatmann, R.; Nazeeruddin, M.K.; Hagfeldt, A. Grätzel, M; Rech, B. Monolithic Perovskite/Silicon-Heterojunction Tandem Solar Cells Processed at Low Temperature. Energ. Environ. Sci. 2016, 9, 81–88. (25) Hou, Y.; Zhang, H.; Chen, W.; Chen, S.; Quiroz, Cesar Omar Ramirez; Azimi, H.; Osvet, A.; Matt, G. J.; Zeira, E.; Seuring, J.; Kausch-Busies, N.; Lövenich, W.; Brabec, C.J. Inverted, Environmentally Stable Perovskite Solar Cell with a Novel Low-Cost and Water-Free PEDOT Hole-Extraction Layer. Adv. Energ. Mat. 2015, 5, 1500543. (26) Liu, M.; Johnston, M. B.; Snaith, H. J. Efficient Planar Heterojunction Perovskite Solar Cells by Vapour Deposition. Nature 2013, 501, 395–398. (27) Wojciechowski, K.; Saliba, M.; Leijtens, T.; Abate, A.; Snaith, H. J. Sub-150 °C Processed Meso-Superstructured Perovskite Solar Cells with Enhanced Efficiency. Energ. Environ. Sci. 2014, 7, 1142–1147. (28) Kim, B. J.; Kim, D. H.; Lee, Y.-Y.; Shin, H.-W.; Han, G. S.; Hong, J. S.; Mahmood, K.; Ahn, T. K.; Joo, Y.-C.; Hong, K. S.; Park, N.-G.; Lee, S.; Jung, H.S. Highly Efficient and


26

Page 27 of 31

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


Bending Durable Perovskite Solar Cells: Toward a Wearable Power Source. Energ. Environ. Sci. 2015, 8, 916–921. (29) Wu, Y.; Yang, X.; Chen, H.; Zhang, K.; Qin, C.; Liu, J.; Peng, W.; Islam, A.; Bi, E.; Ye, F.; Yin, M.; Zhang, P.; Han, L. Highly Compact TiO2 Layer for Efficient Hole-Blocking in Perovskite Solar Cells. Appl. Phys. Express 2014, 7, 52301. (30) Kim, I. S.; Haasch, R. T.; Cao, D. H.; Farha, O. K.; Hupp, J. T.; Kanatzidis, M. G.; Martinson, A. B. F. Amorphous TiO2 Compact Layers via ALD for Planar Halide Perovskite Photovoltaics. ACS Appl. Mater. Inter. 2016, 8, 24310–24314. (31) Werner, J.; Dubuis, G.; Walter, A.; Löper, P.; Moon, S.-J.; Nicolay, S.; Morales-Masis, M.; Wolf, S. de; Niesen, B.; Ballif, C. Sputtered Rear Electrode with Broadband Transparency for Perovskite Solar Cells. Sol. Energ. Mat. Sol. C. 2015, 141, 407–413. (32) Yates, H. M.; Afzaal, M.; Walter, A.; Hodgkinson, J. L.; Moon, S.-J.; Sacchetto, D.; Bräuninger, M.; Niesen, B.; Nicolay, S.; McCarthy, M.; Pemble, M.E.; Povey, I.M.; Balif, C. Progression Towards High Efficiency Perovskite Solar Cells via Optimisation of the Front Electrode and Blocking Layer. J. Mater. Chem. C 2016, 4, 11269–11277. (33) Yang, D.; Yang, R.; Zhang, J.; Yang, Z.; Liu, S.; Li, C. High Efficiency Flexible Perovskite Solar Cells Using Superior Low Temperature TiO2. Energ. Environ. Sci. 2015, 8, 3208–3214. (34) Qiu, W.; Paetzold, U. W.; Gehlhaar, R.; Smirnov, V.; Boyen, H.-G.; Tait, J. G. Conings, B.; Zhang, W.; Nielsen, C. B.; McCulloch, I.; Froyen, L.; Heremans, P.; Cheyns, D. An Electron


27


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 31

Beam Evaporated TiO2 Layer for High Efficiency Planar Perovskite Solar Cells on Flexible Polyethylene Terephthalate Substrates. J. Mat. Chem. A 2015, 3, 22824–22829. (35) Jaysankar, M; Qiu, W.; van Eerden, M; Aernouts, T; Gehlhaar, R.; Debucquoy, M.; Paetzold, U. W.; Poortmans, J. Four-Terminal Perovskite/Silicon Multijunction Solar Modules. Adv. Energ. Mat. 2017, 24, 1602807. (36) Pichot, F.; Pitts, J. R.; Gregg, B. A. Low-Temperature Sintering of TiO2 Colloids: Application to Flexible Dye-Sensitized Solar Cells. Langmuir 2000, 16, 5626–5630. (37) Yamaguchi, T.; Tobe, N.; Matsumoto, D.; Arakawa, H. Highly Efficient Plastic Substrate Dye-Sensitized Solar Cells Using a Compression Method for Preparation of TiO2 Photoelectrodes. Chem. Commun. 2007, 4767–4769. (38) Tebby, Z.; Babot, O.; Toupance, T.; Park, D.-H.; Campet, G.; Delville, M.-H. LowTemperature UV-Processing of Nanocrystalline Nanoporous Thin TiO2 Films: An Original Route toward Plastic Electrochromic Systems. Chem. Mater. 2008, 20, 7260–7267. (39) Habibi, M.; Zabihi, F.; Ahmadian-Yazdi, M. R.; Eslamian, M. Progress in Emerging Solution-Processed Thin Film Solar Cells – Part II: Perovskite Solar Cells. Renew. Sust. Energ. Rev. 2016, 62, 1012–1031. (40) Hwang, K.; Jung, Y.-S.; Heo, Y.-J.; Scholes, F. H.; Watkins, S. E.; Subbiah, J.; Jones, D. J.; Kim, D.-Y.; Vak, D. Toward Large Scale Roll-to-Roll Production of Fully Printed Perovskite Solar Cells. Adv. Mater. 2015, 27, 1241–1247.


28

Page 29 of 31

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


(41) Shin, S. S.; Yang, W. S.; Noh, J. H.; Suk, J. H.; Jeon, N. J.; Park, J. H.; Kim, J. S.; Seong, W. M.; Seok, S. I. High-Performance Flexible Perovskite Solar Cells Exploiting Zn2SnO4 Prepared in Solution Below 100 Degrees C. Nat. Commun. 2015, 6, 7410. (42) Di Giacomo, F.; Zardetto, V.; D'Epifanio, A.; Pescetelli, S.; Matteocci, F.; Razza, S.; Di Carlo, A.; Licoccia, S.; Kessels, W. M. M.; Creatore, M.; Bronw, T.M. Flexible Perovskite Photovoltaic Modules and Solar Cells Based on Atomic Layer Deposited Compact Layers and UV-Irradiated TiO2 Scaffolds on Plastic Substrates. Adv. Energ. Mat. 2015, 5, 1401808. (43) Di Giacomo, F.; Zardetto, V.; Lucarelli, G.; Cinà, L.; Di Carlo, A.; Creatore, M.; Brown, T. M. Mesoporous Perovskite Solar Cells and the Role of Nanoscale Compact Layers for Remarkable All-Round High Efficiency under both Indoor and Outdoor Illumination. Nano Energy 2016, 30, 460–469. (44) Mundus, M. Ultrashort Laser Pulses for Electrical Characterization of Solar Cells; Ph.D. Thesis, University of Konstanz, Germany, 2016. (45) Lee, S.-W.; Kim, S.; Bae, S.; Cho, K.; Chung, T.; Mundt, L. E.; Lee, S.; Park, S.; Park, H.; Schubert, M. C., Glunz, S.W.; Ko, Y.; Jun, Y. Kang, Y.; Lee, H.-S.; Kim, D. UV Degradation and Recovery of Perovskite Solar Cells. Sci. Reports 2016, 6, 38150. (46) Breitwieser, M.; Heinz, F. D.; Büchler, A.; Kasemann, M.; Schön, J.; Warta, W.; Schubert, M. C. Analysis of Solar Cell Cross Sections with Micro-Light Beam Induced Current (µLBIC). Sol. Energ. Mat. Sol. C. 2014, 131, 124–128. (47) Gundel, P.; Heinz, F. D.; Schubert, M. C.; Giesecke, J. A.; Warta, W. Quantitative carrier Lifetime Measurement with Micron Resolution. J. Appl. Phys. 2010, 108, 33705.


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Page 30 of 31

(48) Eperon, G. E.; Moerman, D.; Ginger, D. S. Anticorrelation between Local Photoluminescence and Photocurrent Suggests Variability in Contact to Active Layer in Perovskite Solar Cells. ACS Nano 2016, 10, 10258-10266. (49) Giordano, F.; Abate, A.; Correa Baena, J. P.; Saliba, M.; Matsui, T.; Im, S. H.; Zakeeruddin, S. M.; Nazeeruddin, M. K.; Hagfeldt, A., Graetzel, M. Enhanced Electronic Properties in Mesoporous TiO2 via Lithium Doping for High-Efficiency Perovskite Solar Cells. Nat. Comm. 2016, 7, 10379. (50) Anaraki, E. H.; Kermanpur, A.; Steier, L.; Domanski, K.; Matsui, T.; Tress, W.; Saliba, M.; Abate, A.; Grätzel, M.; Hagfeldt, A.; Correa Baena, J. P. Highly Efficient and Stable Planar Perovskite Solar Cells by Solution-Processed Tin Oxide. Energ. Environ. Sci. 2016, 9, 31283134. (51) Kegelmann, L.; Wolff, C. M.; Awino, C.; Lang, F.; Unger, E. L.; Korte, L.; Dittrich, T.; Neher, D.; Rech, B.; Albrecht, S. It Takes Two to Tango - Double-Layer Selective Contacts in Perovskite Solar Cells for Improved Device Performance and Reduced Hysteresis. ACS Appl. Mater. Inter. 2017, 9, 17245-17255. (52) Mundt, L. E.; Heinz, F. D.; Albrecht, S.; Mundus, M; Saliba, M.; Correa Baena, J. P.; Anaraki, E. H.; Korte, L.; Grätzel, M.; Hagfeldt, A.; Rech, B.; Schubert, M. C.; Glunz, S. W. Non-Destructive Probing of Perovskite Silicon Tandem Solar Cells Using Multi-Wavelength Photoluminescence Mapping. IEEE J. Photovolt. 2017, PP.


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Novel Low-Temperature Process for Perovskite Solar Cells with a

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