Potential Applications of Halide Double Perovskite CsAgInX (X = Cl, Br) in Flexible Optoelectronics: Unusual Effects of Uniaxial Strains.

The discovery of halide double perovskite CsAgInX (X = Cl, Br) has provided an efficient way to search promising solar cell absorbers. Here, theoretical calculations on strained CsAgInX (X = Cl, Br) not only comprehensively and firstly help understand their physical properties but also provide a guideline to extend their potential applications. Although CsAgInX possesses a similar structure, the variations of physical properties of strained CsAgInX are different. Only compressive CsAgInBr undergoes a direct-to-indirect transition, which enables it to be a good radiation detection material. Moreover, the mobility of CsAgInCl is reduced by strains, while that of CsAgInBr is enhanced (reduced) by compression (tension). That is because the contribution degrees of Ag-d , d and In-d , d on the band edges of CsAgInX (X = Cl, Br) are inconsistent. In addition, the absorption coefficients of CsAgInX (X = Cl, Br) are deteriorated negligibly by strain, making it a potential material for further applications of photovoltaics and flexible optoelectronics.