Nations Sean, Jia Ting, Wang Shengnian, Duan Yuhua
National Energy Technology Laboratory, United States Department of Energy Pittsburgh Pennsylvania 15236 USA
Chemical Engineering Department, Louisiana Tech, University Ruston Louisiana 71272 USA
RSC Adv. 2021 Jun 23;11(36):22264-22272. doi: 10.1039/d1ra01586a. eCollection 2021 Jun 21.
Lead halide perovskites have generated considerable interest in solar cell, sensor, and electronics applications. While great focus has been placed on (CHNH)PbI, an organic-inorganic hybrid perovskite, comparatively little work has been done to understand some of its existing crystal phases and analogous materials after substituting with Sn and/or other halogens in the framework. Here, first-principles density functional theory calculations are performed to comprehensively evaluate the electronic and optical properties of (CHNH)BX (B = Sn, Pb; X = F, Cl, Br, I) in a low-temperature orthorhombic phase. Bulk modulus, electronic structures, and several optical properties of these perovskite systems are further calculated. The obtained results are first confirmed by comparing with existing perovskite systems in literature. The shifting trends on those physical properties when extending to other barely studied systems of (CHNH)BX is further revealed. The band gap of these perovskites is found to decrease when varying halogen anion in "X" sites from F to I, and/or substituting Pb cations with Sn in "B" sites. Notably, the less toxic Sn-containing perovskites, (CHNH)SnI in particular, display higher absorption coefficients in the visible light range than their Pb-containing counterparts. An orthorhombic (CHNH)PbF is predicted to exist at low temperature, and adsorb strongly UV energy. Our systematical examination efforts on the two groups of perovskites provide valuable physical insights in these materials, and the accompanied new findings warrant further investigation on such subjects.
卤化铅钙钛矿在太阳能电池、传感器及电子应用领域引发了广泛关注。尽管人们对有机 - 无机杂化钙钛矿（CHNH）PbI投入了大量关注，但对于其在框架结构中用Sn和/或其他卤素替代后的一些现有晶相及类似材料，相关研究相对较少。在此，我们进行了第一性原理密度泛函理论计算，以全面评估低温正交相中（CHNH）BX（B = Sn，Pb；X = F，Cl，Br，I）的电子和光学性质。进一步计算了这些钙钛矿体系的体模量、电子结构及几种光学性质。所得结果首先通过与文献中现有的钙钛矿体系进行比较得以证实。当扩展到（CHNH）BX的其他鲜有研究的体系时，这些物理性质的变化趋势也进一步被揭示。研究发现，当“X”位点的卤素阴离子从F变为I，和/或在“B”位点用Sn替代Pb阳离子时，这些钙钛矿的带隙会减小。值得注意的是，毒性较小的含Sn钙钛矿，尤其是（CHNH）SnI，在可见光范围内比其含Pb对应物表现出更高的吸收系数。预测低温下会存在正交结构的（CHNH）PbF，且其对紫外能量有强烈吸收。我们对这两组钙钛矿的系统研究为这些材料提供了有价值的物理见解，同时这些新发现也值得对该主题进行进一步研究。
