Engineering bandgap of CsPbI3 over 1.7 eV with enhanced stability and transport properties

Potential multijunction application of CsPbI3 perovskite with silicon solar cells to reach efficiencies beyond the Shockley-Queisser limit motivates tremendous efforts to improve its phase stability and further enlarge its band gap between 1.7 and 1.8 eV. Current strategies to increase band gap via conventional mixed halide engineering are accompanied by detrimental phase segregation under illumination. Here, ethylammonium(EA) in a relatively small fraction (x < 0.15) is first investigated to fit into three-dimensional CsPbI3 framework to form pure-phase hybrid perovskites with enlarged band gap over 1.7 eV. The increase of band gap is closely associated with the distortion of Pb-I octahedra and the variation of the average Pb-I-Pb angle. Meanwhile, the introduction of EA can retard the crystallization of perovskite and tune the perovskite structure with enhanced phase stability and transport properties.

Automated summary

Introducing a small fraction of ethylammonium into the CsPbI3 perovskite lattice can form pure-phase hybrid perovskites with an enlarged band gap over 1.7 eV. This results in distortion of Pb-I octahedra and variation of the average Pb-I-Pb angle, while also retarding perovskite crystallization and enhancing phase stability and transport properties.