Ultrafast Amplified Spontaneous Emission Dynamics in Hybrid Perovskites

Methylammonium lead iodide (MAPI) has received significant interest due to high performance of this material in photovoltaic applications. MAPI is also now known to be an efficient light emitter, due in part to its high mobility and long carrier diusion lengths, which make it a good solar cell. Specifically at reduced temperatures, the light emission process is quite interesting. Specifically at low temperatures due to coexistence of multiple crystal phases, energy and charge transfer dynamics play a significant role in light emission process. At room temperature the crystal structure is tetrogonal, whereas at low temperatures material goes through a phase change to orthorombic crystal structure. However even below the phase transition temperatures, the thin films exhibit tetragonal domain inclusions. Since the tetragonal phase has lower bandgap, most excitations diffuse to these low eenrgy sites and recombine. In this work we studied exciton and charge relaxation dynamics that lead to amplified spontaneous emission (ASE) in MAPI. Our results indicate that reveal the duration of the ASE process and the dynamics that limits ASE in MAPI thin films.