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Computational, thin-film deposition, and characterization approaches have been used to investigate the all-inorganic lead-free CsBi3I10 as a candidate to act as a thin-film photovoltaic absorber. In this paper, CsBi3I10 was firstly predicted with a layer crystal structure of stable hexagonal phase-like Cs3Bi2I9 and then prepared by one-step coating also showing the high purity hexagonal phase and crystallinity, very consistent with the theoretical calculation. After solvent annealing, a high absorption coefficient of approximately 105 cm–1 in visible light and a suitable optical band gap of 1.78 eV were obtained for the CsBi3I10 thin film. The solar cell based on the CsBi3I10 perovskite thin film exhibited a high power conversion efficiency of 1.05%, good reproducibility, hysteresis-free behavior, and long-term stability. These results indicate that the performance of all-inorganic Pb-free perovskite solar cells can be further improved.

Abstract:In this work, we report the reproducible preparation method of highly uniform large-area perovskite CH 3 NH 3 PbI 3 thin films by scalable single-source thermal evaporation with the area of 100 cm 2 . The microstructural and optical properties of large-area CH 3 NH 3 PbI 3 thin films were investigated. The dense, uniform, smooth, high crystallinity of large-area perovskite thin film was obtained. The element ratio of Pb/I was close to the ideal stoichiometric ratio of CH 3 NH 3 PbI 3 thin film. These films show a favorable bandgap of 1.58 eV, long and balanced carrier-diffusion lengths. The CH 3 NH 3 PbI 3 thin film perovskite solar cell shows a stable efficiency of 7.73% with almost no hysteresis, indicating a single-source thermal evaporation that is suitable for a large area perovskite solar cell.

We provided a new method to improve the efficiency of Sb2S3 thin film solar cells. The TiO2 electron transport layers were doped by lithium to improve their charge extraction properties for the thermal-evaporated Sb2S3 solar cells. The Mott-Schottky curves suggested a change of energy band and faster charge transport in the Li-doped TiO2 films. Compared with the undoped TiO2, Li-doped mesoporous TiO2 dramatically improved the photo-voltaic performance of the thermal-evaporated Sb2S3 thin film solar cells, with the average power conversion efficiency (PCE) increasing from 1.79% to 4.03%, as well as the improved open-voltage (Voc), short-circuit current (Jsc) and fill factors. The best device based on Li-doped TiO2 achieved a power conversion efficiency up to 4.42% as well as a Voc of 0.645 V, which are the highest values among the reported thermal-evaporated Sb2S3 solar cells. This study showed that Li-doping on TiO2 can effectively enhance the charge extraction properties of electron transport layers, offering a new strategy to improve the efficiency of Sb2S3-based solar cells.

Hybrid two-dimensional (2D) halide perovskites has been widely studied due to its potential application for high performance perovskite solar cells. Understanding the relationship between microstructural and opto-electronic properties is very important for fabricating high-performance 2D perovskite solar cell. In this work, the effect of solvent annealing on grain growth was investigated to enhance the efficiency of photovoltaic devices with 2D perovskite films based on (BA)2(MA)3Pb4I13 prepared by single-source thermal evaporation. Results show that solvent annealing with the introduction of solvent vapor can effectively enhance the crystallization of the (BA)2(MA)3Pb4I13 thin films and produce denser, larger-crystal grains. The thin films also display a favorable band gap of 1.896 eV, which benefits for increasing the charge-diffusion lengths. The solvent-annealed (BA)2(MA)3Pb4I13 thin-film solar cell prepared by single-source thermal evaporation shows an efficiency range of 2.54–4.67%. Thus, the proposed method can be used to prepare efficient large-area 2D perovskite solar cells.