Exploring Charge Transport, Trap States, and Activation Energy of High-Quality CsPbBr3 Single Crystal Grown by Inverse Temperature Crystallization for Photodetector Applications

Abstract

Hybrid organic–inorganic lead halide perovskites have emerged as outstanding semiconducting materials for next-generation optoelectronic devices owing to their long carrier diffusion lengths, high absorption coefficient, tunable optical bandgaps, and low-cost solution processability. However, the organic moiety in these materials is highly susceptible to heat and intense light illumination, which restricts their long-term operational stability. In contrast, all-inorganic cesium-based halide perovskites such as CsPbBr3 exhibit superior thermal and environmental stability, making them attractive candidates for photodetector applications. Herein, we report the growth of high-quality CsPbBr3 single crystals (SCs) using the inverse temperature crystallization (ITC) method and systematically investigate their charge transport properties, trap state density, and ionic activation energy. Space-charge-limited current (SCLC) measurements on the as-grown CsPbBr3 SC reveal a low trap density of 4.61 × 109 cm–3 and a remarkably high charge carrier mobility of 1323 cm2 V–1 s–1, indicating excellent crystalline quality and low defect concentration. Furthermore, temperature-dependent electrochemical impedance spectroscopy (EIS) and temperature-dependent current–voltage (I–V) measurements yield activation energies of 0.27 and 0.32 eV, respectively, which are attributed to the migration of bromide ions/vacancies in the CsPbBr3 lattice. The CsPbBr3 SC-based photodetectors exhibit a stable and reproducible photoresponse when exposed to 525 nm green illumination. They exhibit a responsivity of 0.065 A W–1, a detectivity of approximately 1010 Jones, and an external quantum efficiency of about 15% at a bias of 6 V. Our findings demonstrate that the ITC-grown CsPbBr3 SC combines low trap density, high carrier mobility, and well-defined ionic transport, making it a promising candidate for high-performance, thermally stable SC perovskite photodetectors.