Cl-doped FAPbBr3 single crystals with stabilized lattice and suppressed surface vacancies for environmentally stable photodetectors

Abstract

Halide perovskites are emerging as promising materials for photodetection due to their outstanding optoelectronic properties. However, polycrystalline thin films often suffer from significant defects and high dark currents caused by the abundance of grain boundaries, which hinder efficient carrier transport. In contrast, FAPbBr₃ perovskite single crystals, with their low defect density and high carrier mobility, are widely used in optoelectronic devices. However, when FAPbBr₃ single crystals are exposed to air for a long time, many vacancies are typically generated on the surface, which will capture oxygen from the air. This study found that Cl element doping can prevent FAPbBr₃ single crystals from oxidizing, making them highly stable in air. In addition, chlorine (Cl) can extend the growth window of single crystals, allowing the growth of high-quality single crystals at lower temperatures. The resulting FAPbBr_2.9Cl_0.1 crystals exhibited a resistivity as low as 5.104 × 10⁹ Ω cm, a carrier mobility–lifetime product as high as 3.104 × 10⁻² cm² V⁻¹, a defect density as low as 5.81 × 10⁹ cm⁻³, and an on/off ratio of up to 2288.27 at a bias voltage of 2 V. These properties highlight the potential of chlorine-doped FAPbBr₃ single crystals for high-performance photodetector applications.