Lead-Free Perovskite Cs2CuBr4 Single Crystals: Synthesis and Properties

Abstract

Lead-based perovskites have been one of the hottest research topics due to its excellent optoelectronic performance, such as outstanding absorption coefficients, tuneable bandgap≈1.6 eV, long carrier diffusion length, high defect tolerance, convenient solution processability, and good charge carrier mobility. It has been widely studied to be applied on solar cells, photodetector, and light emitting diode. However, there are still some challenges on widely applying lead halide perovskites: nature toxicity of lead, unreliability in moisture and light environment, poor stability to heat and oxygen, and the existed self-degradation pathway. To overcome these problems, we fabricated lead-free perovskites Cs2CuBr4 single crystals and characterized the perovskites from structure, optical properties, and electrical device performance. The solution-evaporated method was introduced to grow Cs2CuBr4 single crystals. The prepared perovskites exhibit 2D orthorhombic structure and blue-green luminescence with the PL peak at 460nm. The bandgap is ~1.74 eV, which is relatively ideal for optoelectronic devices. Moreover, the resistive switching devices based on Cs2CuBr4 single crystals thin films were also fabricated, showing the excellent reversible threshold switching behaviour and robustness of 2D Cs2CuBr4 material. We believe this thesis significantly demonstrated that lead-free Cs2CuBr4 perovskites have potential to play an important role in the next-generation optoelectronic devices.