Strain-relaxed tetragonal MAPbI3 results in efficient mesoporous solar cells

• DOI: 10.1016/j.nanoen.2021.105788
• Publication Date: 2021-01-19T04:11:49Z
• Authors: Tao Ye; Kai Wang; Shaoyang Ma; Congcong Wu; Yuchen Hou; Dong Yang; Ke Wang; Shashank Priya
• Keywords: Tetragonal crystal system

Abstract In mesoporous organo-halide perovskite solar cells, the coexistence of tetragonal phase and cubic phase in the perovskite layer is found to result in strained crystal structure at the mesoporous TiO2 (mp-TiO2)/perovskite heterointerface. This results in structural defects pinholes, grain boundaries, and interfacial porosity which is detrimental towards photovoltaic performance and device stability. The strain at the interface originates from the lattice mismatch between the mp-TiO2 nanoparticles (NPs) and perovskite. Here, a transformative approach is demonstrated to realize relaxed and high purity tetragonal phase MAPbI3 (RP) near the mp-TiO2 interface region. This approach involves inserting a ~2 nm lattice matched buffer layer of cubic CsPbBr3 between mp-TiO2 NPs and MAPbI3, which serves as a template for epitaxial growth for top MAPbI3. The solar cell with relaxed MAPbI3 shows a power conversion efficiency (PCE) of 22.12% with significantly enhanced environmental, light, and thermal stability.