High-performance ultraviolet Cs3Cu2I5 photodetector derived from two-step annealing process

Abstract

Perovskite based ultraviolet photodetectors have great potential in fire warning, disease treatment and missile guidance, etc. owing to its high mobility, large absorption coefficient and solution processability. However, poor stability and toxic lead element hinder it further applications in current stage. Recently, all-inorganic lead-free perovskite Cs3Cu2I5 demonstrates great potential in ultraviolet detection for its outstanding long-term stability and suitable bandgap. Nevertheless, pinholes and roughness of film lead to leakage current and lower carrier mobility, restricting detection performance. Herein, a two-step annealing method was introduced to optimize the nucleation and crystallization of Cs3Cu2I5 grains. Owing to the improvement of grain quality, fewer pinholes and precipitated phases occurred during crystallization process, thus, resulting in compact and smooth film surface. The hole and electron mobilities of the two-step annealed film were promoted up to 0.697 cm2/(V·s) and 1.579 cm2/(V·s) respectively. As a consequence, the constructed Cs3Cu2I5 photodetector exhibits high on/off ratio of 6.3 × 104, a shorter response time of 26.2 ms (τrise)/49.9 ms (τfall), external quantum efficiency of 3.04%, moderate responsivity of 8.46 mA/W and detectivity of 3 × 1013 Jones. Basing on these merits, an ultraviolet imaging was demonstrated. This work provides an effective but simple strategy to endow Cs3Cu2I5 photodetector with improved performance for further applications in the future.