Widely Tunable, Room Temperature, Single-Mode Lasing Operation from Mixed-Halide Perovskite Thin Films

Solution-processed organic-inorganic hybrid perovskites have recently emerged as promising low-cost materials for optoelectronic applications. However, exposure to light or applied bias causes phase separation of mixed-halide perovskites into iodide-rich domains, resulting in the shift of the bandgap energy toward the infrared for light-emitting devices. Proper selection of self-assembled and bulky organoammonium halide additives, 4-fluorobenzylammonium iodide bromide, FPMAI_1-xBr_x, to the mixed-halide perovskite system, Cs_xMA_1-xPb[I_1-xBr_x]₃ (0 ≤ x ≤ 1), exhibits stronger emission and enables stable and low threshold amplified spontaneous emission, which can be tuned over a wide spectral range. Finally, optically pumped surface-emitting distributed feedback lasers operating in a wide spectral range at room temperature are demonstrated for the first time. The laser emission wavelength can be tuned from green to near-infrared by varying the halide stoichiometry in the mixed-halide perovskites. Ultrasmooth mixed-halide perovskites on fused quartz gratings achieve spatially coherent single-mode laser emission with a pump threshold of 4 μJ/cm² and less than 0.65 nm full-width at half maximum. The laser device lifetime lasts for up to 42 h (∼10⁶ laser pulses) under sustained excitation. This work represents a proof-of-concept laser device for practical use in various applications.