Mitigating Ion Migration in a Mixed-Halide Perovskite via Laser Shock Annealing

Mixed-halide perovskites are susceptible to ion migration due to their high lattice flexibility, resulting in a decrease in device efficiency and the degradation of device stability. In this work, by utilizing the unique pulse characteristics and thermal effects of the nanosecond laser shock annealing (LSA) technique, we can effectively inhibit ionic migration in mixed-halide perovskites, which in turn ameliorates the optoelectronic properties of perovskites. The results show that, compared with traditional thermal annealing (TA), the perovskite films treated by LSA exhibit a more uniform ionic distribution, eliminating the nonphotoactive δ-phase caused by ionic segregation. The reduction in ionic migration is attributed to the enhanced interaction among the inter-ionic forces in the inorganic framework and the optimization of crystallization kinetics in a mixed-halide perovskite, resulting from the ultrafast shock pressure in the range of 0.95-1.64 GPa and the rapid heating/cooling thermal effects of LSA. Furthermore, the perovskite fabricated by LSA significantly reduces the defect density, mitigating defect-driven ionic migration. Therefore, the photophysical processes of perovskites were optimized, which extended the carrier lifetime and enhanced the carrier mobility. In conclusion, the LSA technique provides an efficient approach to addressing the problem of ion migration in mixed-halide perovskites by modulation of the crystal structure and ionic interactions.