Carrier Dynamics in 2D PEA₂PbBr₄ Perovskite: Impact of Exciton–Phonon Interaction and Exciton–Exciton Annihilation

Two-dimensional (2D) perovskites (PVSKs) are promising for photoelectric applications due to their superior optoelectronic properties. However, the presence of self-trapped excitons (STEs), resulting from a strong polaron effect via exciton–phonon (E–P) interaction, significantly impacts their performance. This study employs various optical spectroscopy analyses to explore how the polaronic E–P interaction influences the dynamics of carriers in phenethylammonium lead bromide (PEA2PbBr4). Low-temperature photoluminescence (PL) measurements reveal that the recombination processes are mainly influenced by free excitons and self-trapped excitons, with a correlation between lattice strain and the polaronic E–P interaction. The in-depth analysis of time-resolved photoluminescence (TRPL) implies that diminished polaronic E–P interactions not only enhance the FE recombination rate but also increase the detrapping rate of STE by lowering potential barriers in the detrapping process. On the other hand, we find that the simulation threshold value of amplified spontaneous emission (ASE) is highly dependent on the exciton–exciton annihilation (EEA) process compared to the nonradiative recombination induced via polaronic E–P interaction and the Auger recombination. This study contributes to the progression of our comprehension of exciton transition mechanisms in 2D PVSKs and establishes a correlation between the polaronic E–P interaction and carrier dynamics.