Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093 Zürich, Switzerland.
Empa-Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland.
Nano Lett. 2023 Mar 8;23(5):1914-1923. doi: 10.1021/acs.nanolett.2c04927. Epub 2023 Feb 28.
The long search for nontoxic alternatives to lead halide perovskites (LHPs) has shown that some compelling properties of LHPs, such as low effective masses of carriers, can only be attained in their closest Sn(II) and Ge(II) analogues, despite their tendency toward oxidation. Judicious choice of chemistry allowed formamidinium tin iodide (FASnI) to reach a power conversion efficiency of 14.81% in photovoltaic devices. This progress motivated us to develop a synthesis of colloidal FASnI NCs with a concentration of Sn(IV) reduced to an insignificant level and to probe their intrinsic structural and optical properties. Intrinsic FASnI NCs exhibit unusually low absorption coefficients of 4 × 10 cm at the first excitonic transition, a 190 meV increase of the band gap as compared to the bulk material, and a lack of excitonic resonances. These features are attributed to a highly disordered lattice, distinct from the bulk FASnI as supported by structural characterizations and first-principles calculations.
长期以来，人们一直在寻找无毒的卤化铅钙钛矿（LHP）替代品，研究表明，尽管 Sn(II) 和 Ge(II) 卤化物钙钛矿容易被氧化，但它们的一些引人注目的特性，如载流子的低有效质量，只能在它们最接近的 Sn(II) 和 Ge(II) 类似物中实现。明智的化学选择使得甲脒碘化锡（FASnI）在光伏器件中达到了 14.81%的功率转换效率。这一进展促使我们开发了一种具有低浓度 Sn(IV)的胶体 FASnI NCs 的合成方法，并对其内在的结构和光学性质进行了研究。本征 FASnI NCs 在第一个激子跃迁处表现出异常低的吸收系数，为 4×10cm，与体材料相比，带隙增加了 190 meV，并且没有激子共振。这些特征归因于高度无序的晶格，这与结构表征和第一性原理计算所支持的体 FASnI 不同。
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