Heterojunction‐Depleted Lead‐Free Perovskite Solar Cells with Coarse‐Grained B‐γ‐CsSnI₃ Thin Films

Abstract

Perovskite solar cells (PSCs) have been emerging as a breakthrough photovoltaic technology, holding unprecedented promise for low‐cost, high‐efficiency renewable electricity generation. However, potential toxicity associated with the state‐of‐the‐art lead‐containing PSCs has become a major concern. The past research in the development of lead‐free PSCs has met with mixed success. Herein, the promise of coarse‐grained B‐γ‐CsSnI3 perovskite thin films as light absorber for efficient lead‐free PSCs is demonstrated. Thermally‐driven solid‐state coarsening of B‐γ‐CsSnI3 perovskite grains employed here is accompanied by an increase of tin‐vacancy concentration in their crystal structure, as supported by first‐principles calculations. The optimal device architecture for the efficient photovoltaic operation of these B‐γ‐CsSnI3 thin films is identified through exploration of several device architectures. Via modulation of the B‐γ‐CsSnI3 grain coarsening, together with the use of the optimal PSC architecture, planar heterojunction‐depleted B‐γ‐CsSnI3 PSCs with power conversion efficiency up to 3.31% are achieved without the use of any additives. The demonstrated strategies provide guidelines and prospects for developing future high‐performance lead‐free PVs.

High‐Quality Cs2AgBiBr6 Double Perovskite Film for Lead‐Free Inverted Planar Heterojunction Solar Cells with 2.2 % Efficiency

“…[48] It is also found that the crystallinity of Cs 2 AgBiBr 6 film is able to be improved, which is evidenced by the fact that the intensity of XRD diffraction peaks of Cs 2 AgBiBr 6 film increase as the postannealing temperature increases (Figure 3k). [49] We further test the photovoltaic performance of the Cs 2 AgBiBr 6 film prepared by the anti-solvent dropping method, and a series of inverted planar heterojunction PSCs with the structure of indium tin oxide (ITO)/Cu-NiO/Cs 2 AgBiBr 6 /C 60 /bathocuproine (BCP)/Ag are fabricated (Figure 3m). Moreover, the average grain sizes of the films are determined by analyzing the statistics of grain size in SEM images ( Figure S8).…”

Highly Reproducible Sn‐Based Hybrid Perovskite Solar Cells with 9% Efficiency

“…[12,13] In an attempt to improve the PCE, research efforts have been directed towards optimization of the tin-perovskite film morphology, tuning the film composition, use of a reducing agent, and modification of the device structure. [14][15][16][17][18][19][20][21] The main challenges for further improving the PCE lie in preventing the easy formation of Sn vacancies due to their small formation energy and the fast oxidation of divalent Sn 2+ into more stable Sn 4+ . This causes high levels of self-p-doping in Sn-based perovskite films, with consequent severe recombination losses for charge carriers.…”

Progress of Lead‐Free Halide Double Perovskites

“…Mixed-halide and mixed-cation perovskites have been investigated to address these issues. [23,[33][34][35][37][38][39][40] In addition, the easy oxidation of Sn and Ge from the +2 state to the +4 state due to their high energy 5s and 4s orbitals makes them less promising for application in stable and long-term PSCs. However, the device performance through this approach has fallen short of the Pb-based ones.…”