Supporting Information Tailoring of Electron Collecting Oxide Nano-Particulate Layer for Flexible Perovskite Solar Cells Seong Sik Shin 1,2,, Woon Seok Yang 1,3,, Eun Joo Yeom 1,4, Seon Joo Lee 1, Nam Joong Jeon 1 Young-Chang Joo 2, Ik Jae Park 2, Jun Hong Noh 1,* and Sang Il Seok 1,3,* 1 Division of Advanced Materials, Korea Research Institute of Chemical Technology, 4 Gajeong-Ro, Yuseong-Gu, Daejeon 305-600, Korea 2 Department of Materials Science and Engineering, Seoul National University, Seoul 151-744, Korea 3 School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Eonyang-eup, Ulju-gun, Ulsan 689-798, Korea. 4 Department of Energy Science, 2066 Seoburo, Jangan-gu, Sungkyunkwan University, Suwon 440-746, Republic of Korea These authors contributed equally to this work.
Experimental Synthesis of ZSO particles. All chemicals for the preparation of particles were of regent grade and were used without further purification. ZnCl 2 (12.8 mmol, Aldrich) and SnCl 4 5H 2 O (6.4 mmol, Aldrich) were dissolved in deionized water (160 ml) under vigorous magnetic stirring. N 2 H 4 H 2 O (N 2 H 4 /Zn molar ratio=12) was then added to the reaction solution. After 20 min of stirring, the mixture was transferred to titanium autoclave, which was kept at a temperature between 120 and 200 o C for 6 h in an electric oven. Then the autoclave was cooled to ambient temperature naturally. The resultant precipitates were centrifuged, washed with deionized water and ethanol and re-dispersed in 2 methoxy ethanol, resulting in a colloidal solution. The concentration of the colloidal solution is 12 mg/1ml. Solar cell fabrication. ZSO films were prepared by spin coating the colloidal dispersion of various-sized ZSO particles onto indium tin oxide (ITO) coated glass/poly ethylene naphthalate (PEN) substrate at 3000 rpm for 30 s. To control film thickness, the procedure was repeated 6 times without any dry processes. After baking at 100 C for 1 h in air, the perovskite layer was deposited onto the resulting ZSO film by a consecutive two-step spin coating process at 1000 and 5000 rpm for 10 s and 20 s, respectively, from the mixture solution of methylammonium iodide (CH 3 NH 3 I) and PbI 2. During the second spin coating step, the film was treated with toluene drop-casting, and then was dried on a hot plate at 100 C for 10 min. The detailed preparation of the CH 3 NH 3 I has been described in previous work 19. A solution of poly(triarylamine) (15 mg, PTAA, EM index, M n = 17,500 g mol -1 in toluene (1.5 ml) was mixed with 15 µl of a solution of lithium bistrifluoromethanesulphonimidate (170 mg) in acetonitrile (1 ml) and 7.5 µl 4-tertbutylpyridine. The resulting solution was spin-coated on the CH 3 NH 3 PbI 3 /Zn 2 SnO 4 thin film
at 3000 rpm for 30 s. Finally, an Au counterelectrode was deposited by thermal evaporation. The active area of the device is 0.16 cm 2 and the area for shadow mask is 0.096 cm 2. Characterization. The crystal structure and phase of the materials was characterized using an X-ray powder diffractometer (XRD; New D8 Advance, Bruker). The morphologies and microstructures were investigated by field emission scanning electron microscopy (FESEM, SU 70, Hitachi). The optical properties of samples were characterized using a uv-vis spectrophotometer (UV 2550, Shimadzu). The J V curves were measured using a solar simulator (Oriel Class A, 91195A, Newport) with a source meter (Keithley 2420) at 100 mw cm 2, AM 1.5 G illumination, and a calibrated Si-reference cell certified by the NREL. The J- V curves were measured by reverse scan (forward bias (1.2 V) => short circuit (0V)) or forward scan (short circuit (0 V) => forward bias (1.2 V)). The step voltage and the delay time were fixed at 10 mv and 40 ms, respectively. The J V curves for all devices were measured by masking the active area with a metal mask 0.096 cm 2 in area. Time-dependent PCE, dark current, impedance and capacitance voltage measurements were conducted with a potentiostat (PGSTAT302N, Autolab). Impedance measurements were carried out at DC bias of V = 0.1 V under 1 sun illumination with the frequency ranging between 1 MHz and 0.01 Hz. Capacitance voltage (CV) measurements were performed at fixed frequency (1 khz), employing the ITO/ZSO/perovskite/Au heterojunction structured devices. All measuremts were performed at room temperature.
Figure S1. TEM images of ZSO QD-1 (5.7 nm), QD-2 (9.3 nm) and NP (19.2 nm). 0.8 Intensity (a. u.) 0.6 0.4 0.2 QD-1 QD-2 NP Figure S2. UV-vis absorption spectra of ZSO QD-1 (5.7 nm), QD-2 (9.3 nm) and NP (19.2 nm). 0.0 200 250 300 350 Wavelength (nm)
100 100 Transmittance (%) 80 60 40 20 0 Bare QD-1 QD-2 NP 400 500 600 700 800 Wavelength (nm) 80 60 40 20 0 Diffused reflectance (%) Figure S3. Transmittance and diffused reflectance spectra of ZSO films composed of QD-1 (5.7 nm), QD-2 (9.3 nm) and NP (19.2 nm) on ITO glass substrate. Figure S4. Average photovoltaic parameters for each 12 PSCs based on QD-1 (5.7 nm), QD- 2 (9.3 nm) and NP (19.2 nm) layer.
Figure S5. Cross-sectional SEM images of the PSC-based on a. QD-1 layer, b. QD-2 layer and c. NP layer Figure S6. Average photovoltaic parameters for each 12 designed ECLs based PSCs.
Figure S7. J-V curves of the PSC based on designed-zso-ecl/ch 3 NH 3 (I 0.9 Br 0.1 ) 3 measured by reverse scans with 10 mv voltage steps and 40 ms delay times under AM 1.5 G illumination. Figure S8. Stabilized PCE of the PSC based on designed-zso-ecl/ch 3 NH 3 (I 0.9 Br 0.1 ) 3 measured close to the maximum power point (~0.926 V).
Figure S9. J-V curves of the flexible PSC based on designed-zso-ecl/ch 3 NH 3 (I 0.9 Br 0.1 ) 3 measured by forward and reverse scans with 10 mv voltage steps and 40 ms delay times under AM 1.5 G illumination. 10 8 Counts 6 4 PCE (%) Figure S10. Histogram of solar cell efficiencies for the 24 designed ZSO ECL-based flexible PSCs. 2 0 10 12 14 16 18 20
Table S1. Photovoltaic parameters of a flexible perovskite solar cell. J sc (ma/cm 2 ) V oc (V) FF η (%) Reverse 20.4 1.1 0.73 16.5 Forward 20.3 1.09 0.56 12.4