Phase distribution management in quasi-2D perovskite films toward highly efficient amplified spontaneous emission pumped by nanosecond pulsed laser

Quasi-two-dimensional (Quasi-2D) perovskites exhibit unique photophysical properties, which make them an excellent candidate for potential advancements in laser technology. Nanosecond pulse laser pumped lasing and amplified spontaneous emission (ASE) with high performance is the key process to realize the continuous wave pumped optically and electrically pumped laser. However, several difficulties still exist in the development ofquasi-2D perovskites ASE or lasing under nanosecond pulsed laser pumping, including the high concentration of surface defects, Auger recombination and inefficient energy transfer. Herein, by an additive-free strategy through Cs⁺ cation doping, the morphology and phase distribution of quasi-2D perovskite films could be well managed and thus the insufficient energy transfer pathway caused by low-n phases was almost entirely resolved. The gain nature and carrier recombination were revealed with fast energy transfer process. Based on this, the net gain coefficient of the PEA₂(FA_0.7Cs_0.3)₂Pb₃Br₁₀ (PEA⁺ = phenylethylammonium; FA⁺ = formamidinium) perovskite films with an appropriate proportion of Cs⁺ cation displayed a nearly three-fold increase than that of the pristine perovskite film, thereby significantly lowering the ASE threshold under nanosecond laser excitation to a third. Our results suggest that the Cs⁺-doped strategy in quasi-2D perovskites could provide insights into the design by phase distribution to realize high-performance laser devices in the future.