溴掺杂对RbPbI $_3$结构、电子和光学性质影响的从头算研究
Ab-initio study of the effect of bromide mixing into RbPbI$_3$ on the structural, electronic and optical properties
摘要：
基于卤化物preovskites的超高效率和成本效益的光致光伏器件为正在进行的光伏研究带来了革命，超出了科学界的期望。然而，结构稳定性是一个严重的问题，阻碍了它们在器件级的大规模集成。具有卤化物混合的组成工程已经成为处理该问题而不损害装置效率的有效方式。在此，使用密度泛函理论计算溴混合正交$\rm{{RbPb(I_{1-x}Br_x)_3}}$（其中，$\rm{x}=0.25$、$0.50$和$0.75$）的结构、电子和光学性质。用PBE（Perdew-Burke-Ernzerhof）势和TB-mBJ（Tran Blaha modified Becke Johnson）势计算了电子能带结构和态密度. PBE和TB-mBJ分别获得了$\rm{x}=0.50$溴混合的最低能隙$2.288$和$2.986$ eV。相比之下，混合溴化物相具有较小的有效质量，有利于更好的载流子传输通过混合卤化物。使用PBE，激子似乎是Mott-Wannier类型。然而，TB-mBJ预测的激子是Frenkel型溴混合的$\rm{x}=0.75$和莫特-万尼尔型的所有其他混合下的研究。对于I和Br的等量混合物，分别使用PBE和TB-mBJ，观察到光谱极限最大效率（SLME）在$14.0$和$4.1$的最高值处。计算的性质与文献报道的类似结构的数据一致。
英文摘要：
The ultra-high efficiency and cost-effective photovoltaics based on halide preovskites have brought a revolution to ongoing photovoltaic research, surpassing the expectations of the scientific community. However, structural stability is a severe issue that hinders their wide-scale integration at the device level. Compositional engineering with the halide mixing has become an efficient way to deal with this issue without compromising device efficiency. Herein, the structural, electronic and optical properties of the bromide mixed orthorhombic $\rm{{RbPb(I_{1-x}Br_x)_3}}$ (where, $\rm{x}=0.25$, $0.50$ and $0.75$) are calculated using the density functional theory. The electronic bandstructure and density of states (DOS) are calculated using both PBE (Perdew-Burke-Ernzerhof) and TB-mBJ (Tran Blaha modified Becke Johnson) potential. The lowest energy bandgaps of $2.288$ and $2.986$ eV for bromide mixing of $\rm{x}=0.50$ are obtained using PBE and TB-mBJ, respectively. In contrast, the mixed bromide phases possess a smaller effective mass, facilitating a better carrier transport through the mixed halide. Using PBE, the excitons appear to be the Mott-Wannier type. However, the TB-mBJ predicts the exciton to be Frenkel type for bromide mixing of $\rm{x}=0.75$ and a Mott-Wannier type for all other mixing under study. The spectroscopic limited maximum efficiency (SLME) is observed to be at the highest values of $14.0$\% and $4.1$\% for the equal admixture of I and Br using PBE and TB-mBJ, respectively. The calculated properties are consistent with the reported data of the similar structures.
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