Laser-Induced Enhancement of Optical Gain and Stability in Potassium-Doped CsPbBr₃ Perovskite Films

In perovskite laser development, it is important to focus on two different regimes of electrical losses: low-power excitation (carrier density lower than 10¹⁸ cm^-3), when nonradiative processes via trap states can dominate, and high-power excitation (carrier density is 10¹⁸-10²¹ cm^-3), when Auger recombination prevails. Therefore, passivating the defects that affect radiative recombination is crucial for lowering the lasing threshold and achieving a high optical gain before the Auger onset. Here, we report a combined laser-induced photothermochemical method for the passivation of surface defects by potassium doping in perovskite. This approach yields improved morphology, an optical gain of up to 2600 cm^-1, and operational stability under ambient conditions of 35 million laser shots, with only 15% degradation at excitation densities three times above the threshold. The remarkable performance of this laser-induced process will facilitate the development of modern optical applications, including lasing, morphology-controlled photoluminescence yield, and optical information encryption.