Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A. This journal is The Royal Society of Chemistry 1 Low-temperature-processed inorganic perovskite solar cells via solvent engineering with enhanced mass transport Huachao Zai, a,b Deliang Zhang, a Liang Li, c Cheng Zhu, a Sai Ma, a Yizhou Zhao, a Zhiguo Zhao, d Changfeng Chen, b Huanping Zhou, c Yujing Li* a and Qi Chen* a a. School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 1, P.R. China b. Department of Materials Science and Engineering, College of Science, China University of Petroleum, Beijing 9, P.R. China c. Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 71, P.R. China d. Clean Energy Research Institute, China Huaneng Group, Beijing 9, P.R. China
Experimental section Materials. All reagents were used as received without further purification, including isopropanol (IPA, 99.99%, Sigma-Aldrich), SnO (15% in H O colloidal dispersion liquid, Alfa Aesar), PbI (99.999%, Sigma-Aldrich), PbBr (99.999%, Sigma-Aldrich), CsI (99.999%, Sigma-Aldrich), N,Ndimethylformamide (DMF, 99.99%, Sigma-Aldrich), Dimethyl sulfoxide (DMSO, 99.9%, Sigma- Aldrich), chlorobenzene (CB, 99.9%, Sigma-Aldrich), PTAA ( 99.5%, Xi an Polymer Light Technology Corp.), bis(trifluoromethane)sulfonimide lithium salt (Li-TFSI, 99.95%, Sigma- Aldrich), -tert-butylpyridine (tbp, 99.9%, Sigma-Aldrich), acetonitrile (ACN, 99.9%, Sigma- Aldrich) and ITO substrates. Fabrication of solar cells. The indium tin oxide (ITO) coated glass was sequentially cleaned using detergent, ultra-pure water, and isopropanol. After 3 minutes of UV-O 3 treatments, the SnO electron transport layers (ETLs) were spin-coated on ITO substrates from the SnO colloidal solutions, and annealed on a hot plate at the displayed temperature of 15 C for 3 min in ambient air. The CsPbI Br precursor solution was prepared in a mixed solvent of DMF and DMSO with different volume ratios. The perovskite films were deposited onto the SnO substrates with one-step spin coating procedures. The step was 3 rpm for 3~15 s. The substrate was then immediately transferred on a hot plate and heated at C for 5 min. After cooling down to room temperature, the hole-transport layer was subsequently deposited on top of the perovskite film by spin coating at 3 rpm for 3 s using a CB solution which contained PTAA, tbp and Li-TFSI. All operations were conducted in ambient atmosphere (temperature: C, relative humidity: %). Finally, nm Au contact was deposited on top of Spiro-OMeTAD by thermal evaporation. Characterizations. The thickness of films was measured with BRUKER DektakXT step profiler. Scanning electron microscope (SEM) images were measured using Hitachi S field-emission scanning electron microscopy. X-ray diffraction (XRD) patterns were recorded by Rigaku D/Max, with Cu Kα as the X-ray source. The UV-visible absorption spectra were measured by Hitachi UH15 spectrophotometer. PL spectra and TRPL spectra were obtained by FLS9 (Edinburgh Instruments Ltd) with an excitation at 5 nm. The J-V measurement was performed via the solar simulator (SS-F5-3A, Enlitech) along with AM 1.5G spectra whose intensity was calibrated by the certified standard silicon solar cell (SRC-, Enlitech) at mw/cm. Light intensity was calibrated with a National Institute of Metrology (China) calibrated KG5-filtered Si reference cell. The scanning speed of all J-V curves is.1 V/s. The effective area of cells were.3 cm and 1. cm defined by masks for all the photovoltaic devices discussed in this work. The external quantum efficiency (EQE) data were obtained by using the solar-cell spectral-response measurement system (QE-R, Enlitech). A calibrated silicon diode with a known spectral response was used as a reference. The absorption and transmission spectra were measured by Hitachi UH15 spectrophotometer.
1: :1 1:1 1: :1 Figure S1. Optical image of perovskite films fabricated with different DMF: DMSO ratios (. M). a b 1..9 PCE (%) Voc (V)..7. c 1 1: :1 1:1 1: :1 d.5 1: :1 1:1 1: :1 11 7 Jsc (ma/cm ) 9 7 FF (%) 5 1: :1 1:1 1: :1 3 1: :1 1:1 1: :1 Figure S. PV metrics for devices (~ cells for each condition) fabricated with different DMF: DMSO ratios (. M). :1 3:1 :1 1:1 1: :1 Figure S3. Optical image of perovskite films fabricated with different DMF: DMSO ratios (. M).
Table S1. Thicknesses of the CsPbI Br films fabricated with different DMF: DMSO ratios (. M). Samples Thicknesses of the CsPbI Br films (nm) Average (nm) :1 33.3 33. 3. 3. 3.7 35.1 3:1 3.7 9. 39.5 3. 37. 3.1 :1 33.17 9.3 3.3 9.1 3. 3.71 1:1.99 97. 91.1 33.9 5.7 9. 1: 31.1 5.7 7. 7.1 7.57 71.9 :1. 9. 3. 3.1 13. 1.79.5 () () FWHM ( )..15 :1 3:1 :1 1:1 1: :1 DMF/DMSO ratios Figure S. FWHM of () and () peaks for perovskite films fabricated with different DMF: DMSO ratios. Intensity (a.u.) Cs-PbX -DMSO CsPbI Br 5 15 5 3 35 ( )
Figure S5. XRD pattern of the as spin-coated film fabricated with DMF/DMSO=/1 before annealing. Table S. Carrier lifetimes for the CsPbI Br films fabricated with different DMF: DMSO ratios. Sample τ 1 (ns) τ (ns) A 1 A τ ave (ns) :1.5.51.93.7.9 3:1 5.15 11.37.9. 5.7 :1.3 1...1 7. 1:1 5.5 11.5.7.13.5 1: 3..37.1.19 3. :1.3.79.5. 3.53 Table S3. Urbach energies for the CsPbI Br films fabricated with different DMF: DMSO ratios. Sample :1 3:1 :1 1:1 1: :1 E u (mev) 1.7 9.9.9 5.5 15. 157.7
a PCE (%) 1 b Voc (V) 1. 1.1 1..9..7 c 15 :1 3:1 :1 1:1 1: :1 d. :1 3:1 :1 1:1 1: :1 1 75 Jsc (ma/cm ) 13 1 11 FF (%) 7 5 55 9 :1 3:1 :1 1:1 1: :1 5 :1 3:1 :1 1:1 1: :1 Figure S. PV metrics for devices (~ cells for each condition) fabricated with different DMF: DMSO ratios (. M). 3s 5s s 9s 1s 15s Figure S7. Optical image of perovskite films fabricated with different spin-coating time. Br L I L Cs L Pb M Figure S. EDX mapping images for a perovskite film fabricated with 1 s.
.5 () () FWHM ( )..15 3 s 5 s s 9 s 1 s 15 s Spin-coating time Figure S9. FWHM of () and () peaks for perovskite films fabricated with different spincoating time. Table S. Thicknesses of the CsPbI Br films fabricated with different spin-coating time. Samples Thicknesses of the CsPbI Br films (nm) Average (nm) 3 s 9.7 31.53 3.7 39. 91.53 3.15 5 s 9. 97.53 39. 91.57 3.5 3. s 31.5 3.5 37.53 9. 3. 31. 9 s 33.17 9.3 3.3 9.1 3. 3.71 1 s 3.5 97.5 3.53 93.7 3. 31.9 15 s 97.19 33.55 97. 35.3 3.3 31.3 Table S5. Carrier lifetimes for the CsPbI Br films fabricated with different spin-coating time. Sample τ 1 (ns) τ (ns) A 1 A τ ave (ns) 3 s.7 13.3.99.1.1 5 s.3 5.71.9.11 3.15 s 3.9.1.7.33. 9 s.3 1...1 7. 1 s.79 1.17.5.35 9.1
15 s. 1.3..3.7 Table S. Urbach energies for the CsPbI Br films fabricated with different spin-coating time. Sample 3 s 5 s s 9 s 1 s 15 s E u (mev) 11.99 1.3 11..9 1.55 73. a 1 b 1. PCE (%) 1 Voc (V) 1.1 1..9..7 c 1 3 s 5 s s 9 s 1 s 15 s d. 3 s 5 s s 9 s 1 s 15 s Jsc (ma/cm ) 1 1 FF (%) 75 7 5 55 3 s 5 s s 9 s 1 s 15 s 5 3 s 5 s s 9 s 1 s 15 s Figure S. PV metrics for devices (~ cells for each condition) fabricated with different different spin-coating time.
Absorbance (a.u.) 3 1 h 3 1 Eg=1.91 ev 1.7 1. 1.9..1. Energy (ev) 5 7 Wavelength (nm) Figure S11. UV-vis absorption spectrum of the perovskite film fabricated with optimal condition, with an inset showing the Tauc plot. Au PTAA CsPbI Br SnO ITO 1 μm Figure S1. Cross-sectional SEM image of the optimal device. a PCE (%) 15 1 13 1 11 This work Ref. 7 Ref. Ref. 5 Ref. Ref. 3 Ref. Ref. 1 b Normalized PCE Ref. 1 1. Ref. Ref. 3 Ref. Ref. 5 1. Ref. 7 This work.. 3 9 1 Time (days) Figure S13. Comparison of (a) PCE and (b) long-term stability for inorganic perovskite solar cells with PCE over % via low-temperature process. 1-7
Intensity (a.u.) After 1 month Initial 3 5 ( ) Figure S1. XRD patterns evolution of the CsPbI Br film heated on a C hotplate in a nitrogen filled glove box. Intensity (a.u.) 3 1 Initial After 1 month 5 7 Wavelength (nm) Figure S15. UV-vis spectra evolution of the CsPbI Br film heated on a C hotplate in in a nitrogen filled glove box. Current density (ma/cm ) 15 5 h-f h-r 1h-F 1h-R..... 1. 1. Voltage (V)
Figure S1. J-V curves for a device measured by forward and reverse scans with a.1 cm active area before and after 1 h under continuous light soaking. 1 PCE (%) 1s, C 1s, C 5s, C Figure S17. PCE for devices (~ cells for each condition) fabricated with different spin-coating time and annealing temperature. (. M) References: 1. C. F. J. Lau, M. Zhang, X. Deng, J. Zheng, J. Bing, Q. Ma, J. Kim, L. Hu, M. A. Green, S. Huang and A. Ho-Baillie, ACS Energy Lett., 17,, 319-35.. Q. Wang, X. Zheng, Y. Deng, J. Zhao, Z. Chen and J. Huang, Joule, 17, 1, 371-3. 3. T. Zhang, M. I. Dar, G. Li, F. Xu, N. Guo, M. Grätzel and Y. Zhao, Science Advances, 17, 3, e171.. Y. Hu, F. Bai, X. Liu, Q. Ji, X. Miao, T. Qiu and S. Zhang, ACS Energy Lett., 17,, 19-7. 5. Y. Wang, T. Zhang, F. Xu, Y. Li and Y. Zhao, Solar RRL, 1,, 171.. C. Liu, W. Li, C. Zhang, Y. Ma, J. Fan and Y. Mai, J. Am. Chem. Soc., 1, 1, 35-3. 7. Y. Jiang, J. Yuan, Y. Ni, J. Yang, Y. Wang, T. Jiu, M. Yuan and J. Chen, Joule, 1,, 135-13.