Unravelling the path to high-performance perovskite lasers : the study and tailoring of optical gain properties

Metal halide perovskites (MHPs) have thus far demonstrated to be remarkable coherent light emitters with high optical gains and broad spectral tunability, which could enable the development of versatile and efficient solution-processed lasers. However, unlocking the full potential of MHPs as gain materials will require a deep understanding and precise optimization of their optical gain properties. The present thesis work addresses these challenges by exploring and tunning the optical gain of different MHPs and their low-dimensional derivatives. As a first step, a methodology is devised for the rigorous characterization of optical gain, involving the variable stripe length method and photoluminescence fluence-dependent measurements. This methodology is scrutinized by studying MAPbI3, a 3D perovskite with notable stimulated emission. The studies reveal a high optical gain coefficient, comparable to traditional III-V semiconductors, as well as a fluence-dependent evolution of the gain spectrum that resembles the behaviour of bulk GaAs. Thereafter, low-dimensional MHP derivatives are investigated, focusing on lead-free 2D MHPs. This thesis takes advantage of the rich chemical diversity of 2D MHPs to control and enhance their optical gain. The study of three distinct 2D MHPs with varying organic cations evidences that the nature of the organic cation plays a crucial role in determining the amplified spontaneous emission (ASE) response. PEA2SnI4 emerges as a standout candidate with low defectivity, high optical gain, and stability, proving its strength as a gain medium in an optically pumped DFB device. These findings emphasize the importance of material design in tunning the optical gain of 2D MHPs. Finally, the thesis examines the optical gain properties of lead-free 3D MHPs, with a focus on FA0.85Cs0.15SnI3 and its temperature-dependent ASE response. A striking shift in ASE threshold is observed at 220 K, marking a transition from weak to strong temperature insensitivity. This remarkable property allows for a consistent ASE operation between 193 and 77 K. On the whole, in this thesis, the optical gain characteristics of MHPs are described and effectively controlled. As such, the work contributes to the development of tailored MHP-based lasers, presenting thrilling avenues for both fundamental research and practical applications.