Optimal Bandgap in a 2D Ruddlesden–Popper Perovskite Chalcogenide for Single-Junction Solar Cells

Abstract

Transition metal perovskite chalcogenides (TMPCs) are explored as stable,\nenvironmentally friendly semiconductors for solar energy conversion. They can\nbe viewed as the inorganic alternatives to hybrid halide perovskites, and\nchalcogenide counterparts of perovskite oxides with desirable optoelectronic\nproperties in the visible and infrared part of the electromagnetic spectrum.\nPast theoretical studies have predicted large absorption coefficient, desirable\ndefect characteristics, and bulk photovoltaic effect in TMPCs. Despite recent\nprogresses in polycrystalline synthesis and measurements of their optical\nproperties, it is necessary to grow these materials in high crystalline quality\nto develop a fundamental understanding of their optical properties and evaluate\ntheir suitability for photovoltaic application. Here, we report the growth of\nsingle crystals of a two-dimensional (2D) perovskite chalcogenide, Ba3Zr2S7,\nwith a natural superlattice-like structure of alternating double-layer\nperovskite blocks and single-layer rock salt structure. The material\ndemonstrated a bright photoluminescence peak at 1.28 eV with a large external\nluminescence efficiency of up to 0.15%. We performed time-resolved\nphotoluminescence spectroscopy on these crystals and obtained an effective\nrecombination time of ~65 ns. These results clearly show that 2D\nRuddlesden-Popper phases of perovskite chalcogenides are promising materials to\nachieve single-junction solar cells.\n