Metal halide perovskite absorbers with wide bandgaps (1.6–1.7 eV) that are suitable for tandem devices typically require high Br concentrations; this renders the material prone to halide segregation and degradation. Inorganic, bromine-free CsPbI3 has a wide bandgap of 1.7 eV and does not suffer from halide segregation; however, these active layers are not stable at room temperature. Here, we report a method to create stable tetragonal perovskites with a bandgap near 1.7 eV: we add small amounts of large A-site cations having ionic radii between 272 and 278 pm—dimethylammonium (DMA) and guanidinium (Gua)—into the crystal lattice. When we deploy perovskites using mixed Cs and these large organic cations, we achieve stable, wide bandgap perovskites with power conversion efficiencies of 15.2% and V_OC of 1.19 V. This study extends materials selection for wide bandgap Cs-based perovskites.

中文翻译：

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通过A-Site阳离子取代，稳定，无溴的四方钙钛矿，带隙为1.7 eV

适用于串联装置的宽带隙（1.6-1.7 eV）的金属卤化物钙钛矿吸收剂通常需要较高的Br浓度；这使得该材料易于卤化物偏析和降解。无机的，不含溴的CsPbI3具有1.7 eV的宽带隙，并且没有卤化物的偏析。但是，这些活性层在室温下不稳定。在这里，我们报告了一种创建带隙接近1.7 eV的稳定四方钙钛矿的方法：将少量具有离子半径在272至278 pm之间的大A位阳离子（二甲基铵（DMA）和胍盐（Gua））添加到晶体中格子。当我们使用混合Cs和这些大的有机阳离子部署钙钛矿，我们实现稳定的，具有15.2％和功率转换效率的宽带隙的钙钛矿V _OC 1.19V。这项研究扩展了宽禁带Cs基钙钛矿的材料选择。