High-Performance, Semitransparent, Easily Tunable Vivid Colorful

Article pubs.acs.org/JPCC

High-Performance, Semitransparent, Easily Tunable Vivid Colorful Perovskite Photovoltaics Featuring Ag/ITO/Ag Microcavity Structures Jong-Hong Lu,* Yan-Lin Yu, Shiou-Ruei Chuang, Chun-Hung Yeh, and Chih-Ping Chen* Department of Materials Engineering, Ming Chi University of Technology, New Taipei City 243, Taiwan S Supporting Information *

ABSTRACT: In this study, we developed semitransparent perovskite (PVSK) photovoltaic (PV) cells with vivid colors, arising from optical interference in the microcavity systems, dependent on the thickness of their indium tin oxide (ITO) optical spacers. After embedding precisely controllable Ag/ ITO/Ag microcavity structures, we obtained PVSK cells exhibiting strong coloration: reddish-orange, orange, yellow, yellow-green, yellowish-green, bluish-green, and blue. We obtained an optimized power conversion efficiency (PCE) of 7.2% for a yellow PVSK device under simulated AM 1.5G irradiation (100 mW cm−2). This device also exhibited high stability: After storage in the dark for 70 day in an Arfilled glovebox, its PCE remained consistently high (up to 7.4%). This approach has potential for use in the preparation of highly efficient, inexpensive, and colorful building-integrated PVs.

■

allow perfect merging with the building.26,27 Employing a colorful absorber layer (e.g., by altering the composition of the halide in a perovskite system) will allow the ready fabrication of colorful devices, but this strategy can reduce the PCEs significantly for low-wavelength color devices as a result of poor light-harvesting. To address these challenges, Lee et al.,26 Armstrong and O’Dwyer,28 and Zhang et al.29 recently developed PVSK-based PV cells in which they exploited strong interference effects, using optical microcavities or photonic crystals, to create various colors. Using these approaches, a single optimized panchromatic active layer can generate a broad range of color hues without sacrificing performance. In this study, we employed a Ag/ITO/Ag microcavity structure that allowed us to vary the transmission of visible light by altering the thickness of the ITO layer sandwiched between the Ag cathodes. Because this structure was formed after fabrication of the PVSK device, it had no impact on the chargecollection efficiency, and we could ignore any interfacial problems.30 Furthermore, the nontransmitted portion of residual light was reflected back to the active layer, thereby enhancing the photocurrent.31,32 Because of the low resistivity and high reflectivity of the silver and the highly pure transparency and color of the resonant cavity structures, we explored and studied the Ag/ITO/Ag colored electrodes for PVSK applications. We employed the inverted architecture ITO/poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS)/CH 3 NH 3 PbI 3−x Cl x /PCBM/Ag/ITO/Ag, where PCBM is phenyl-C61-butyric acid methyl ester, to study the influence of the thicknesses of the PVSK, Ag, and ITO

INTRODUCTION Organic/inorganic lead halide perovskite (PVSK) solar cells have great potential for use in the harvesting of renewable energy, because of their simple preparation through wet-coating processes compatible with roll-to-roll production and, especially, because their power conversion efficiencies (PCEs) can match or even surpass those of today’s best thin-film solar cells.1−9 The evolution of the device architectures of PVSK solar cells, from mesoscopic to planar embodiments, suggests high compatibility and versatility with respect to manufacturing methods.10−16 With advances in device engineering, the PCEs of PVSK solar cells have recently surpassed 20.1% (certified value).1−3,17 The most commonly studied PVSK deviceswith a metal oxide (TiO2, ZnO) as the electron-transport layer inserted between the PVSK layer and an indium tin oxide (ITO) or fluorine-doped tin oxide (FTO) layer and 2,2′,7,7′tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) or a conjugated polymer as the holetransport layer embedded between the PVSK layer and the metal electrodes (Ag, Au)are also relatively stable in air.18−23 Furthermore, Krebs et al. used slot-die roll coating under ambient conditions to prepare PVSK submodules displaying high performance.5 These advances suggest that this technology will soon be ripe for commercialization. Building-integrated photovoltaics (BIPVs) can be employed as replacements for conventional building parts, including roofs, facades (curtain walls, vertical glass), and skylights.24,25 BIPVs used typically as ancillary electrical power sources for saving energy are among the fastest growing products in the PV business. From an aesthetic point of view, a challenge remains to harmoniously integrate such PVs within modern buildings; they must have certain propertiesfor example, semitransparency, desired reflective or transmitted colors, and flexibility to © XXXX American Chemical Society

Received: November 13, 2015 Revised: February 9, 2016

A

DOI: 10.1021/acs.jpcc.5b11144 J. Phys. Chem. C XXXX, XXX, XXX−XXX

Article

The Journal of Physical Chemistry C

Figure 1. Schematic representation of microcavity-based semitransparent PVSK cells and molecular structures of PCBM and lead halide perovskite.

Figure 2. (a) Simulated (dashed lines) and measured (solid lines) spectral transmittance curves of colorful, semitransparent PVSK PV devices. (b) CIE 1931 chromaticity space, presenting the color hues of the microcavity-based RO (0.60, 0.34), Y (0.49, 0.45), YG (0.39, 0.54), YWG (0.23, 0.58), G (0.16, 0.45), and GB (0.15, 0.28) PVSK devices. Digital camera pictures of the devices. Colors (from greenish-blue to reddish-orange) displayed by devices integrating different microcavity structures.

layers on the device performance (Figure 1). Controlling the color of this multilayer structure required a consideration of the optical complex refractive index and thickness of each layer. We

employed the multiple-beam interference (MBI) recursive method to simulate the reflectance and transmittance spectra of the devices.33 Accordingly, we also fabricated corresponding B

DOI: 10.1021/acs.jpcc.5b11144 J. Phys. Chem. C XXXX, XXX, XXX−XXX

Article

The Journal of Physical Chemistry C

91 nm, yellow-green (YG) (0.38, 0.54) at 84 nm, yellowishgreen (YWG) (0.23, 0.59) at 76 nm, green (G) (0.16, 0.45) at 69 nm, and greenish-blue (GB) (0.15, 0.26) at 64 nm. The CIE coordinates shifted from the blue toward the red corner as the ITO layer became thicker. The simulations revealed that altering the thickness of the PVSK did not change the hue, but it did affect the transmission of the colored electrodes (Figure S1, Table S2). To measure the accuracy of the simulation data, we fabricated real devices with the same thicknesses of ITO as used in the simulations. We applied a rotational-sequentialsputtering (RSS) system to precisely control the thickness of each ITO film.36 We employed a dc sputtering power (50 W) to decrease the deposition temperature under a low process O2 gas flow rate (0.25 sccm) and a fixed Ar gas flow rate (50 sccm). During this process, cleaning of the target with Ar gas prior to the sputtering process was necessary to maintain the composition of the ITO surface. Accordingly, we deposited various Ag/ITO/Ag structures by controlling the deposition times, resulting in low sheet resistances of 0.5−0.6 Ω/□. Figure 2a displays the simulated (dotted lines) and measured (solid lines) UV−vis spectra of the colored PVSK devices incorporating a PVSK layer thickness of 75 nm. We observed a consistency between the measured and simulated transmittance spectra, except for the blue-colored sample, for which the simulated bandwidth, peak value, and transmittance were slightly higher than those measured. The sharpest and highest transmittances were those of the reddish-orange devices, primarily because of the relatively lower absorption of PVSK at longer wavelengths.26 Figure 2b presents digital camera images of the devices. To identify the color hues of these microcavity-based PVSK devices, we determined their color coordinates, which are displayed in Figure 2b as colored symbols on the CIE 1931 chromaticity diagram. For ITO thicknesses of 100, 90, 85, 76, 68, and 63 nm, the optical transmittance measurements of the colored electrodes provided color coordinates of RO (0.60, 0.34), Y (0.49, 0.45), YG (0.39, 0.54), YWG (0.23, 0.58), G (0.16, 0.45), and GB (0.15, 0.28), respectively. Thus, the CIE 1931 values of the true and simulated devices were consistent. Accordingly, the colors could be readily manipulated merely by altering the thickness of the ITO layer, such that the microcavity-embedded decorative PVSK cells could produce distinctive vivid transmittance colors. Perovskite Photovoltaic Devices. We fabricated colored PVSK devices having the layered configuration glass/ITO/ PEDOT:PSS/CH3NH3PbI3−xClx/PC61BM/Ag/ITO/Ag, similar to those reported previously (Figure 1a).34,35,37 We prepared the PVSK precursor solution by dissolving MAI and lead(II) chloride (at a molar ratio of 3:1) in DMF. Because of the coverage and inefficient light harvesting of the PVSK active layer, we could not obtain reasonable PCEs for devices featuring a 75-nm PVSK layer; similarly, the PCEs of 100-nm PVSK-based devices were approximately 4%. Hence, we fabricated devices featuring a PVSK thickness of 120 nm to provide a sufficient PCE while ensuring that some of the incident light could reach the Ag/ITO/Ag microcavity cathode to create the transmitted colors. Table 1 summarizes the opencircuit voltages (Voc), short-circuit current densities (Jsc), fill factors (FFs), and PCEs of the devices prepared with cathodes of various thicknesses; the numbers in parentheses are the average device performances determined from four fabricated devices. The PCE of the normal device (100-nm Ag cathode) was 8.9%, with a Jsc value of 14.6 mA cm−2, a Voc value of 0.91 V, and an FF value of 0.67. This PCE was lower than those of

PVSK devices to study the correlation among these conditions, the optical properties, and the performance. The resulting devices displayed vivid transmission colors with an average PCE of 6.5%.

■

EXPERIMENTAL SECTION

Materials and Methods. All chemicals were purchased from Aldrich and used as received, unless otherwise specified. UV−vis absorption spectra were recorded using a Hitachi U5100 spectrophotometer. Device Fabrication and Characterization. Solar cells were prepared using the following device fabrication procedure: Glass/ITO substrates [Sanyo, Osaka, Japan (8 Ω/□)] were sequentially patterned lithographically, cleaned with detergent, ultrasonicated in acetone and isopropyl alcohol, dried on a hot plate at 140 °C for 10 min, and treated with oxygen plasma for 5 min. PEDOT:PSS (Baytron P-VP AI4083) was passed through a 0.45-μm filter prior to deposition on ITO (thickness ≈ 45 nm) by spin-coating (3000 rpm) in air; the sample was then dried at 140 °C for 20 min in a glovebox. The PVSK precursor solution was prepared by dissolving methylammonium iodide (MAI) and lead(II) chloride (3:1, molar ratio) at 25 wt % in dimethylformamide (DMF) and continuously stirring at 60 °C in the dark overnight. PVSK devices, having the layered configuration glass/ITO/PEDOT:PSS/ CH3NH3PbI3−xClx/PC61BM/Ag/ITO/Ag, were fabricated using methods similar to those reported previously.34,35 Prior to the deposition of the PVSK layer, the PEDOT:PSS film was preheated at 60 °C for 5 min. The precursor solution was also preheated at 60 °C for 5 min and then deposited on top of the PEDOT:PSS film. PCBM was spin-coated (2000 rpm) from a chlorobenzene solution (10 mg mL−1). The first layer of Ag (35 nm) was deposited thermally under a vacuum. Precisely controlled ITO and Ag layers were then deposited by rotational sequential sputtering.33 The active area of each device was 10 mm2. The cell performance was measured inside a glovebox. The current−voltage (I−V) properties of the devices were measured under AM 1.5 illumination (100 mW cm−2) using a computer-controlled Keithley 2400 source measurement unit (SMU) and a Newport solar simulator (Oriel Sol2A Class ABA Solar Simulators). The illumination intensity was calibrated using a standard Si reference cell and a KG-5 filter.

■

RESULTS AND DISCUSSION Design and Simulation of Colored Solar Cells. To investigate how the thickness of ITO affected the various hues, we used the MBI recursive method to simulate the transmittance spectra of the devices. By altering the thicknesses of each layer (ITO electrode/PEDOT:PSS/PVSK/PCBM/Ag/ ITO/Ag), we could generate various simulated hues. We set the thicknesses of the ITO electrode, PEDOT:PSS, PCBM, and Ag layers at 150, 30, 50, and 35 nm, respectively, for the calculations (i.e., the same as their thicknesses in the actual devices; Table S1). By altering the thicknesses of the PVSK and ITO layers, we could simulate the predicted hues and transmittances of the colored solar cells. Figure 2a and Figure S1 and Table S2 present the simulated transmission and CIE 1931 coordinates (x, y) (calculated from the simulated transmission spectra) of the colored devices. For devices incorporating 75 nm of PVSK, we observed various simulated colors upon varying the thickness of the ITO layer: reddishorange (RO) (0.58, 0.34) at 101 nm, yellow (Y) (0.50, 0.44) at C

DOI: 10.1021/acs.jpcc.5b11144 J. Phys. Chem. C XXXX, XXX, XXX−XXX

Article

The Journal of Physical Chemistry C Table 1. J−V Characteristics of Colored PVSK Devices device Ag(100 nm) Ag(35 nm) reddish-orange orange yellow yellow-green yellowishgreen bluish-green blue

Jsc (mA cm−2)

Voc (V)

FF (%)

PCE (%)

14.6 14.4 14.8 14.1 14.5 13.8 14.5

0.91 0.88 0.84 0.88 0.91 0.87 0.89

0.67 0.56 0.54 0.58 0.55 0.51 0.53

8.9 7.1 6.7 7.2 7.2 6.1 6.9

(8.6) (7.0) (6.6) (6.8) (6.9) (6.1) (6.8)

7.9/435.8 12.3/445.6 14.1/323.2 15.1/532.2 27.5/350.8 22.8/320.9 34.0/437.1

14.7 14.0

0.85 0.84

0.61 0.48

7.6 (7.0) 5.7 (5.7)

9.5/517.9 15.6/224.0

certain conductivity (for efficient electron collection), we tested the effects of the thickness of the Ag layer on the device performance. Increasing the thickness of the Ag layer caused the PCE to increase but the transmittance of the devices to decrease. Thus, there is a trade-off between the PCE and the transmission efficiency. The optimized performance was that of devices featuring a 35-nm Ag layer, which is reasonably semitransparent while having sufficient conductivity for efficient electron collection. Table 1 lists the PCEs of the PVSK devices featuring a cathode of 35-nm Ag. We observed a decrease in PCE from 8.9% for the 100-nm Ag device to 7.1% for the 35nm Ag device, because of significant lowering of the FF. We calculated the series resistance (Rs) and shunt resistance (Rsh) of each device from the inverse slope of its J−V curve. As revealed in Table 1, the values of Rs for the 100- and 35-nm Ag devices were 7.9 and 12.3 Ω cm2, respectively. The series resistance of a device is related to the resistance of its active layer, the contact resistance between each interfacial layer, and

Rs/Rsh (Ω cm2)

state-of-the-art PVSK devices because the PVSK layer in our design was much thinner than those in other reports.38−40 To allow the incident light to pass through the semitransparent microcavity (to create transmitted colors) and maintain a

Figure 3. (a) Simulated (dashed lines) and measured (solid lines) spectral transmittance curves of the PVSK PV devices. Images of fabricated colored PV devices. The background image can be clearly seen through our fabricated samples with various colors. (b) Current density−potential characteristics of various colored devices under illumination with AM 1.5G solar simulated light (100 mW cm−2). D

DOI: 10.1021/acs.jpcc.5b11144 J. Phys. Chem. C XXXX, XXX, XXX−XXX

Article

The Journal of Physical Chemistry C

Rsh of the colored devices were complex, possibly affected by the conditions for fabricating the PVSK and microcavity structure. The relatively sharp and high transmittance for the RO device was due primarily to the relatively low absorption of PVSK at longer wavelengths.41 The PCE of the RO device was 6.7% with a transmittance of 16%. Because of the requirement for transmittance, the values of Jsc were limited, and hence, they restricted the PCEs. The principle for improving the performance of solar cells is the efficient use of light. The appearance of a solar cell is presented by the color of light that penetrates or reflects; accordingly, we conducted a study to optimize the design of high-performance colored perovskite solar cells. We used the multiple-beam interference (MBI) recursive method to calculate the theoretical (spectral) transmittance of our solar cell structures.33,36 The MBI recursive method is an approach for computing the overall wave optics interference of multilayer thin films, based on the assumption of optical coherency. The results are presented in terms of the probability of the incident light wave reflecting (reflectivity) or penetrating (transmittance). This methodology has very good applicability when simulating uniform multilayer thin films.33,36 Herein, we report the first example of the use of Ag/ITO/Ag microcavity structures to prepare colored perovskite devices, with high consistency between the spectral measurements and theoretical simulations. Because of the low sheet resistance and high reflectivity of the Ag/ITO/Ag resonator, we obtained PCEs of up to 7.6%. We suspect that optimizing the reflectance might further increase the performance of such devices. Further development of these devicesto better understand the relationship between the optics and the device performance and structure and to increase the PCEis currently under investigation in our laboratory. Long-term stability is the greatest challenge affecting the commercial application of PVSK-based PV devices. To further demonstrate the advantages of incorporating microcavity structures in colored solar cells, we studied the degradation of these devices over time.35,42,43 To evaluate the stability of these colored devices, we stored them inside a glovebox so that the effects of water could be ignored (thereby avoiding the uncertainty of encapsulation). We examined the stability of our 100-nm Ag device along with the Y, YG, O, and BG colored devices. Figure 4 and Table S3 summarize the PCEs of the

the resistance of the electrode contacts. Thus, the resistances (in this case, the contact resistance and electrode resistance) of our 100-nm Ag-derived device were relatively low, and as a result, we obtained a higher FF. The corresponding slight decrease in the value of Rsh, from 435.8 to 445.6 Ω cm2, suggests similar levels of defects leading to charge recombination and the leakage current. In a previous study, Lin and coworkers investigated Ag/N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine (NPB)/Ag as an efficient microcavity structure for colored organic solar cells; they suggested that the bottom Ag layer of the microcavity structure functioned as a semitransparent reflector and photocarrier collector.30 The thickness of the bottom Ag layers is the dominant factor determining the lateral conductivity and the series resistance of such a device. In the present study, the bottom Ag layer (underlying thin metal layer of the microcavity structure) collected the photogenerated carriers, which were then transported through the ITO layer to the outer contacting Ag layer, from which we measured the efficiency. The ITO layer acted mainly as a transmittance modulating layer; ideally, the electrical properties (e.g., Voc, FF) of the resulting colored devices should be independent of the structure of the Ag/ITO/ Ag colored electrodes. Notably, this 35-nm Ag film served as a protection layer for the following sputtering process; typically, the PCEs of these PVSK devices would be determined after such processing. We fabricated colored PVSK devices using the conditions determined from our simulations. We recorded the pictures and the UV−vis spectra using a sample size of 1.5 cm × 1.5 cm. We measured the power conversion efficiency of a device having an active area of 0.2 cm × 0.5 cm. We obtained a variety of colorful PVSK devices with CIE 1931 coordinates that were RO (0.63, 0.34), orange (O) (0.59, 0.40), Y (0.48, 0.50), YG (0.42, 0.54), YWG (0.27, 0.63), bluish-green (BG) (0.16, 0.45), and blue (B) (0.22, 0.19) (Figure S2). The colors of the optical transmittances of the devices varied with respect to the ITO thicknesses in a manner consistent with the simulation data: RO at 103 nm, O at 95 nm, Y at 88 nm, YG at 84 nm, YWG at 76 nm, BG at 64 nm, and B at 53 nm. The color changes of the red, blue, and green devices were dependent on the thickness of the ITO layer through Ag−ITO−Ag resonator control; Figure 3a presents the simulated (dashed lines) and measured (solid lines) spectral transmittance curves for these devices. Similar to the behavior of the 75-nm devices, the sharpest and highest transmittances were those of the reddish-orange devices. Photographs of the devices taken with a digital camera revealed the various colors (from blue to reddish-orange; Figure S2) obtainable when integrating the different microcavity structures. From a comparison of the images of the 75- and 120-nm devices (Figure 2b and Figure S2), we observed the distribution of color shades for the thicker PVSK devices. The change in film quality might have influenced the optical complex refractive index (n, k), thereby resulting in slight differences between the experimental and simulated transmittance spectra. Regardless, we could indeed control the color of the perovskite devices. We observed the highest PCE of 7.6% for the BG device, along with a Jsc value of 14.7 mA cm−2, a Voc value of 0.85 V, and an FF value of 0.61 (Table 1, Figure 3b). The average PCEs of these devices were greater than 6.5%, with average transmittances of approximately 8%. After applying the microcavity structure, we observed an increase in the series resistances in the color devices, relative to that of the 100-nm Ag device. The effects on the variations of the values of Rs and

Figure 4. Long-term performance of the PVSK cells. E

DOI: 10.1021/acs.jpcc.5b11144 J. Phys. Chem. C XXXX, XXX, XXX−XXX

Article

The Journal of Physical Chemistry C

Fabricated through Intramolecular Exchange. Science 2015, 348, 1234−1237. (2) Jeon, N. J.; Noh, J. H.; Yang, W. S.; Kim, Y. C.; Ryu, S.; Seo, J.; Seok, S. I. Compositional Engineering of Perovskite Materials for High-Performance Solar Cells. Nature 2015, 517, 476−80. (3) 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. (4) Espinosa, N.; Serrano-Luján, L.; Urbina, A.; Krebs, F. C. Solution and Vapour Deposited Lead Perovskite Solar Cells: Ecotoxicity from a Life Cycle Assessment Perspective. Sol. Energy Mater. Sol. Cells 2015, 137, 303−310. (5) Schmidt, T. M.; Larsen-Olsen, T. T.; Carlé, J. E.; Angmo, D.; Krebs, F. C. Upscaling of Perovskite Solar Cells: Fully Ambient Roll Processing of Flexible Perovskite Solar Cells with Printed Back Electrodes. Adv. Energy Mater. 2015, 5, 1500569. (6) Huang, L.; Hu, Z.; Xu, J.; Zhang, K.; Zhang, J.; Zhu, Y. Multi-Step Slow Annealing Perovskite Films for High Performance Planar Perovskite Solar Cells. Sol. Energy Mater. Sol. Cells 2015, 141, 377− 382. (7) Yan, K.; Long, M.; Zhang, T.; Wei, Z.; Chen, H.; Yang, S.; Xu, J. Hybrid Halide Perovskite Solar Cell Precursors: Colloidal Chemistry and Coordination Engineering Behind Device Processing for High Efficiency. J. Am. Chem. Soc. 2015, 137, 4460−4468. (8) Kaltenbrunner, M.; Adam, G.; Glowacki, E. D.; Drack, M.; Schwodiauer, R.; Leonat, L.; Apaydin, D. H.; Groiss, H.; Scharber, M. C.; White, M. S.; et al. Flexible High Power-Per-Weight Perovskite Solar Cells with Chromium Oxide-Metal Contacts for Improved Stability in Air. Nat. Mater. 2015, 14, 1032−9. (9) Xu, M.-F.; Zhang, H.; Zhang, S.; Zhu, H. L.; Su, H.-M.; Liu, J.; Wong, K. S.; Liao, L.-S.; Choy, W. C. H. A Low Temperature Gradual Annealing Scheme for Achieving High Performance Perovskite Solar Cells with No Hysteresis. J. Mater. Chem. A 2015, 3, 14424−14430. (10) Yu, Y. Y.; Chiang, R. S.; Hsu, H. L.; Yang, C. C.; Chen, C. P. Perovskite Photovoltaics Featuring Solution-Processable Tio2 as an Interfacial Electron-Transporting Layer Display to Improve Performance and Stability. Nanoscale 2014, 6, 11403−10. (11) Bai, Y.; Yu, H.; Zhu, Z.; Jiang, K.; Zhang, T.; Zhao, N.; Yang, S.; Yan, H. High Performance Inverted Structure Perovskite Solar Cells Based on a PCBM:Polystyrene Blend Electron Transport Layer. J. Mater. Chem. A 2015, 3, 9098−9102. (12) Heo, J. H.; Han, H. J.; Kim, D.; Ahn, T. K.; Im, S. H. HysteresisLess Inverted CH3NH3PbI3 Planar Perovskite Hybrid Solar Cells with 18.1% Power Conversion Efficiency. Energy Environ. Sci. 2015, 8, 1602−1608. (13) Wu, Y.; Islam, A.; Yang, X.; Qin, C.; Liu, J.; Zhang, K.; Peng, W.; Han, L. Retarding the Crystallization of PbI2for Highly Reproducible Planar-Structured Perovskite Solar Cells Via Sequential Deposition. Energy Environ. Sci. 2014, 7, 2934−2938. (14) Liu, M.; Johnston, M. B.; Snaith, H. J. Efficient Planar Heterojunction Perovskite Solar Cells by Vapour Deposition. Nature 2013, 501, 395−398. (15) You, J.; Hong, Z.; Yang, Y. M.; Chen, Q.; Cai, M.; Song, T. B.; Chen, C. C.; Lu, S.; Liu, Y.; Zhou, H.; et al. Low-Temperature Solution-Processed Perovskite Solar Cells with High Efficiency and Flexibility. ACS Nano 2014, 8, 1674−80. (16) Saliba, M.; Tan, K. W.; Sai, H.; Moore, D. T.; Scott, T.; Zhang, W.; Estroff, L. A.; Wiesner, U.; Snaith, H. J. Influence of Thermal Processing Protocol Upon the Crystallization and Photovoltaic Performance of Organic−Inorganic Lead Trihalide Perovskites. J. Phys. Chem. C 2014, 118, 17171−17177. (17) Stranks, S. D.; Snaith, H. J. Metal-Halide Perovskites for Photovoltaic and Light-Emitting Devices. Nat. Nanotechnol. 2015, 10, 391−402. (18) Leo, K. Perovskite Photovoltaics: Signs of Stability. Nat. Nanotechnol. 2015, 10, 574−575. (19) Mei, A.; Li, X.; Liu, L.; Ku, Z.; Liu, T.; Rong, Y.; Xu, M.; Hu, M.; Chen, J.; Yang, Y.; et al. A Hole-Conductor-Free, Fully Printable

devices with respect to time. The initial PCEs of the 100 nm Ag, Y, YG, O, and BG devices were 8.6%, 7.2%, 6.1%, 7.2%, and 6.9%, respectively (Table S3). The PCE of the 100-nm Ag device increased from 8.6% to 10% over the first few weeks and then decayed to 8.3% after 70 days. The Y cell exhibited excellent stability after storage for 70 days, maintaining its performance with a PCE of 7.4%, a Jsc value of 14.7 mA cm−2, a Voc value of 0.90 V, and an FF value of 56.0%. The YG and BG devices displayed similar behavior, with 70-day PCEs of 6.4 and 7.1%, respectively (Table S3). In this study, we applied an additional procedure (a rotational-sequential-sputtering process) for depositing the microcavity structures on top of the PVSK devices. These measurements confirmed the stability of such colored solar cells and implies that the particular Ag/ITO/ Ag microcavity structure does not alter the long-term stability of the devices.

■

CONCLUSIONS We have simulated and fabricated colored PVSK PV devices featuring microcavity structures through precise control over the thickness of their Ag/ITO/Ag electrodes. The advantages of this fabrication approach are that the structural color is unlikely to bleach or change over time and that the performance of the devices is not limited by the need for various colorful absorber layers. Furthermore, any optimized panchromatic PVSK layers can be readily integrated with a broad range of vivid colors. We observed a PCE of 7.1% for a yellow PVSK device with extremely high stabilitylong-term storage in the dark in an Ar-filled glovebox for over 70 days provided consistently high PCEs (up to 7.4%). Thus, the microcavity structure appears to stabilize the interface for highperformance BIPV applications. Further improvements should be possible by optimizing the fabrication conditions and enhancing the values of Jsc and PCE of the device through the fine-tuning of the reflectance bands of PVSK to allow better light harvesting from the Ag/ITO/Ag structure.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jpcc.5b11144. Simulation parameters, CIE coordinates (x, y) of the devices, simulated spectral transmittance curves, and time evolution of long-term PCEs (%) (PDF)

■

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. Fax: 886-2-29084091. Tel.: 886-2-29089899 + 4678. *E-mail: [email protected]. Fax: 886-2-29084091. Tel.: 886-2-29089899 + 4439. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS We thank the Ministry of Science and Technology of Taiwan (MOST 103-2113-M-131-001-MY2, MOST 104-2119-M-002016-) for financial support.

■

REFERENCES

(1) Yang, W. S.; Noh, J. H.; Jeon, N. J.; Kim, Y. C.; Ryu, S.; Seo, J.; Seok, S. I. High-Performance Photovoltaic Perovskite Layers F

DOI: 10.1021/acs.jpcc.5b11144 J. Phys. Chem. C XXXX, XXX, XXX−XXX

Article

The Journal of Physical Chemistry C Mesoscopic Perovskite Solar Cell with High Stability. Science 2014, 345, 295−8. (20) Niu, G.; Guo, X.; Wang, L. Review of Recent Progress in Chemical Stability of Perovskite Solar Cells. J. Mater. Chem. A 2015, 3, 8970−8980. (21) Burschka, J.; Pellet, N.; Moon, S.-J.; Humphry-Baker, R.; Gao, P.; Nazeeruddin, M. K.; Gratzel, M. Sequential Deposition as a Route to High-Performance Perovskite-Sensitized Solar Cells. Nature 2013, 499, 316−319. (22) Kim, H.-S.; Im, S. H.; Park, N.-G. Organolead Halide Perovskite: New Horizons in Solar Cell Research. J. Phys. Chem. C 2014, 118, 5615−5625. (23) Carretero-Palacios, S.; Calvo, M. E.; Míguez, H. Absorption Enhancement in Organic−Inorganic Halide Perovskite Films with Embedded Plasmonic Gold Nanoparticles. J. Phys. Chem. C 2015, 119, 18635−18640. (24) Wen, L.; Chen, Q.; Sun, F.; Song, S.; Jin, L.; Yu, Y. Theoretical Design of Multi-Colored Semi-Transparent Organic Solar Cells with Both Efficient Color Filtering and Light Harvesting. Sci. Rep. 2014, 4, 7036. (25) Deng, Y.; Wang, Q.; Yuan, Y.; Huang, J. Vividly Colorful Hybrid Perovskite Solar Cells by Doctor-Blade Coating with Perovskite Photonic Nanostructures. Mater. Horiz. 2015, 2, 578−583. (26) Lee, K.-T.; Fukuda, M.; Joglekar, S.; Guo, L. J. Colored, Seethrough Perovskite Solar Cells Employing an Optical Cavity. J. Mater. Chem. C 2015, 3, 5377−5382. (27) Lee, J. Y.; Lee, K.-T.; Seo, S.; Guo, L. J. Decorative Power Generating Panels Creating Angle Insensitive Transmissive Colors. Sci. Rep. 2014, 4, 4192. (28) Armstrong, E.; O’Dwyer, C. Artificial Opal Photonic Crystals and Inverse Opal Structures - Fundamentals and Applications from Optics to Energy Storage. J. Mater. Chem. C 2015, 3, 6109−6143. (29) Zhang, W.; Anaya, M.; Lozano, G.; Calvo, M. E.; Johnston, M. B.; Míguez, H.; Snaith, H. J. Highly Efficient Perovskite Solar Cells with Tunable Structural Color. Nano Lett. 2015, 15, 1698−1702. (30) Chen, Y.-H.; Chen, C.-W.; Huang, Z.-Y.; Lin, W.-C.; Lin, L.-Y.; Lin, F.; Wong, K.-T.; Lin, H.-W. Microcavity-Embedded, ColourTuneable, Transparent Organic Solar Cells. Adv. Mater. 2014, 26, 1129−1134. (31) Lin, H.-W.; Chiu, S.-W.; Lin, L.-Y.; Hung, Z.-Y.; Chen, Y.-H.; Lin, F.; Wong, K.-T. Device Engineering for Highly Efficient TopIlluminated Organic Solar Cells with Microcavity Structures. Adv. Mater. 2012, 24, 2269−2272. (32) Ren, X.; Li, X.; Choy, W. C. H. Optically Enhanced SemiTransparent Organic Solar Cells through Hybrid Metal/Nanoparticle/ Dielectric Nanostructure. Nano Energy 2015, 17, 187−195. (33) Lu, J. H.; Chen, B. Y. Colored Hard Coatings with AlN-TiN Multilayer Structures. J. Vac. Sci. Technol., A 2014, 32, 02B106. (34) Hsu, H. L.; Chang, C. C.; Chen, C. P.; Jiang, B. H.; Jeng, R. J.; Cheng, C. H. High-Performance and High-Durability Perovskite Photovoltaic Devices Prepared Using Ethylammonium Iodide as an Additive. J. Mater. Chem. A 2015, 3, 9271−9277. (35) Hsu, H.-L.; Chen, C.-P.; Chang, J.-Y.; Yu, Y.-Y.; Shen, Y.-K. Two-Step Thermal Annealing Improves the Morphology of SpinCoated Films for Highly Efficient Perovskite Hybrid Photovoltaics. Nanoscale 2014, 6, 10281. (36) Lu, J.-H.; Chen, B.-Y.; Wang, C.-H. Investigation of Nanostructured Transparent Conductive Films Grown by RotationalSequential-Sputtering. J. Vac. Sci. Technol., A 2014, 32, 02B107. (37) Hsu, H.-L.; Juang, T.-Y.; Chen, C.-P.; Hsieh, C.-M.; Yang, C.-C.; Huang, C.-L.; Jeng, R.-J. Enhanced Efficiency of Organic and Perovskite Photovoltaics from Shape-Dependent Broadband Plasmonic Effects of Silver Nanoplates. Sol. Energy Mater. Sol. Cells 2015, 140, 224−231. (38) Chen, Q.; De Marco, N.; Yang, Y.; Song, T.-B.; Chen, C.-C.; Zhao, H.; Hong, Z.; Zhou, H.; Yang, Y. Under the Spotlight: The Organic−Inorganic Hybrid Halide Perovskite for Optoelectronic Applications. Nano Today 2015, 10, 355−396.

(39) Stranks, S. D.; Nayak, P. K.; Zhang, W.; Stergiopoulos, T.; Snaith, H. J. Formation of Thin Films of Organic−Inorganic Perovskites for High-Efficiency Solar Cells. Angew. Chem., Int. Ed. 2015, 54, 3240−3248. (40) Wu, C.-G.; Chiang, C.-H.; Tseng, Z.-L.; Nazeeruddin, M. K.; Hagfeldt, A.; Gratzel, M. High Efficiency Stable Inverted Perovskite Solar Cells without Current Hysteresis. Energy Environ. Sci. 2015, 8, 2725−2733. (41) Hsu, H.-L.; Chang, C.-C.; Chen, C.-P.; Jiang, B.-H.; Jeng, R.-J.; Cheng, C.-H. High-Performance and High-Durability Perovskite Photovoltaic Devices Prepared Using Ethylammonium Iodide as an Additive. J. Mater. Chem. A 2015, 3, 9271−9277. (42) Reese, M. O.; Gevorgyan, S. A.; Jørgensen, M.; Bundgaard, E.; Kurtz, S. R.; Ginley, D. S.; Olson, D. C.; Lloyd, M. T.; Morvillo, P.; Katz, E. A.; et al. Consensus Stability Testing Protocols for Organic Photovoltaic Materials and Devices. Sol. Energy Mater. Sol. Cells 2011, 95, 1253−1267. (43) Chen, C.-P.; Chen, Y.-D.; Chuang, S.-C. High-Performance and Highly Durable Inverted Organic Photovoltaics Embedding SolutionProcessable Vanadium Oxides as an Interfacial Hole-Transporting Layer. Adv. Mater. 2011, 23, 3859−3863.

G

DOI: 10.1021/acs.jpcc.5b11144 J. Phys. Chem. C XXXX, XXX, XXX−XXX