Department of Chemistry and Biochemistry , University of Oklahoma , 101 Stephenson Parkway , Norman , Oklahoma 73019 , United States.
Homer L. Dodge Department of Physics & Astronomy , University of Oklahoma , 440 W. Brooks Street , Norman , Oklahoma 73019 , United States.
Inorg Chem. 2019 Apr 1;58(7):4446-4455. doi: 10.1021/acs.inorgchem.8b03623. Epub 2019 Feb 15.
Replacement of the toxic heavy element lead in metal halide perovskites has been attracting a great interest because the high toxicity and poor air stability are two of the major barriers for their widespread utilization. Recently, mixed-cation double perovskite halides, also known as elpasolites, were proposed as an alternative lead-free candidate for the design of nontoxic perovskite solar cells. Herein, we report a new nontoxic and air stable lead-free all-inorganic semiconductor RbAgBiBr prepared using the mixed-cation approach; however, RbAgBiBr adopts a new structure type (Pearson's code oP32) featuring BiBr octahedra and AgBr square pyramids that share common edges and corners to form a unique 2D layered non-perovskite structure. RbAgBiBr is also demonstrated to be thermally stable with the measured onset decomposition temperature of T = 520 °C. Optical absorption measurements and density functional theory calculations suggest a nearly direct band gap for RbAgBiBr. Room temperature photoluminescence (PL) measurements show a broadband weak emission. Further, temperature-dependent and power-dependent PL measurements show a strong competition between multiple emission centers and suggest the coexistence of defect-bound excitons and self-trapped excitons in RbAgBiBr.
在金属卤化物钙钛矿中替代有毒重金属元素铅引起了极大的关注，因为高毒性和较差的空气稳定性是限制其广泛应用的两个主要障碍。最近，混合阳离子双钙钛矿卤化物，也称为钙钛矿，被提议作为设计无毒钙钛矿太阳能电池的无铅替代品。在此，我们报告了一种新的无毒且空气稳定的无铅全无机半导体 RbAgBiBr，它是使用混合阳离子方法制备的；然而，RbAgBiBr 采用了一种新的结构类型（Pearson 码 oP32），其特征是 BiBr 八面体和 AgBr 四方锥共享共同的边缘和角落，形成独特的 2D 层状非钙钛矿结构。RbAgBiBr 还被证明具有热稳定性，测量的起始分解温度为 T = 520°C。光吸收测量和密度泛函理论计算表明 RbAgBiBr 具有近直接带隙。室温光致发光（PL）测量显示宽带弱发射。此外，温度和功率依赖性 PL 测量表明多个发射中心之间存在强烈竞争，并表明 RbAgBiBr 中存在缺陷束缚激子和自陷激子的共存。
