Sansom Harry C, Longo Giulia, Wright Adam D, Buizza Leonardo R V, Mahesh Suhas, Wenger Bernard, Zanella Marco, Abdi-Jalebi Mojtaba, Pitcher Michael J, Dyer Matthew S, Manning Troy D, Friend Richard H, Herz Laura M, Snaith Henry J, Claridge John B, Rosseinsky Matthew J
University of Liverpool, Department of Chemistry, Crown Street, Liverpool L69 7ZD, U.K.
University of Oxford, Clarendon Laboratory, Department of Physics, Parks Road, Oxford OX1 3PU, U.K.
J Am Chem Soc. 2021 Mar 17;143(10):3983-3992. doi: 10.1021/jacs.1c00495. Epub 2021 Mar 8.
Since the emergence of lead halide perovskites for photovoltaic research, there has been mounting effort in the search for alternative compounds with improved or complementary physical, chemical, or optoelectronic properties. Here, we report the discovery of CuAgBiI: a stable, inorganic, lead-free wide-band-gap semiconductor, well suited for use in lead-free tandem photovoltaics. We measure a very high absorption coefficient of 1.0 × 10 cm near the absorption onset, several times that of CHNHPbI. Solution-processed CuAgBiI thin films show a direct band gap of 2.06(1) eV, an exciton binding energy of 25 meV, a substantial charge-carrier mobility (1.7 cm V s), a long photoluminescence lifetime (33 ns), and a relatively small Stokes shift between absorption and emission. Crucially, we solve the structure of the first quaternary compound in the phase space among CuI, AgI and BiI. The structure includes both tetrahedral and octahedral species which are open to compositional tuning and chemical substitution to further enhance properties. Since the proposed double-perovskite CsAgBiI thin films have not been synthesized to date, CuAgBiI is a valuable example of a stable Ag/Bi octahedral motif in a close-packed iodide sublattice that is accessed via the enhanced chemical diversity of the quaternary phase space.
自从卤化铅钙钛矿用于光伏研究以来，人们一直在加大力度寻找具有改进或互补物理、化学或光电性能的替代化合物。在此，我们报告了CuAgBiI的发现：一种稳定的无机无铅宽带隙半导体，非常适合用于无铅串联光伏电池。我们在吸收起始点附近测量到非常高的吸收系数为1.0×10 cm，是CHNHPbI的几倍。溶液处理的CuAgBiI薄膜显示出2.06(1) eV的直接带隙、25 meV的激子结合能、较高的电荷载流子迁移率(1.7 cm V s)、较长的光致发光寿命(33 ns)以及吸收和发射之间相对较小的斯托克斯位移。至关重要的是，我们解析了CuI、AgI和BiI相空间中第一种四元化合物的结构。该结构包括四面体和八面体物种，它们易于进行成分调整和化学取代以进一步增强性能。由于迄今尚未合成所提出的双钙钛矿CsAgBiI薄膜，CuAgBiI是在紧密堆积的碘化物亚晶格中稳定的Ag/Bi八面体 motif的一个有价值的例子，它是通过四元相空间增强的化学多样性获得的。
