Exciton-Phonon-Plasmon Interplay in Hot Carrier Relaxation Dynamics in Perovskite Crystals

Enhancing light-matter interaction in nanostructures using metallic surface plasmons is a dependable route for improving efficiencies in optoelectronic applications. Plasmonic interfaces of organic cation-based halide perovskites that show high quantum efficiency and enhanced carrier lifetimes are seen as a technologically important avenue for new-age photovoltaics and quantum emitters. Here, several interesting multi-particle interplays in hybrid structures of Ga nanodroplets and FAPbBr₃ crystals (Ga-NCs) having novel practical applications are reported. In addition to the conventional emission enhancement, a dominant blueshift in the perovskite photoluminescence (PL) is seen in the presence of Ga nanoparticles, which are persistent down to low temperatures. The integrated PL intensity ratio has a non-monotonic temperature dependence indicating a non-trivial exciton-phonon-plasmon interplay. The time-resolved photoluminescence measurements at different excitation wavelengths and transient absorption measurements reveal the strong influence of the Ga nanoparticles on the intrinsic phonon bottleneck typically observed in FAPbBr₃ crystals (NCs). Detailed calculations explain the observed results throwing light on the complex interplay of plasmons, excitons, and the phonons in these simple heterojunctions. Ga-supported perovskite nanocrystals with higher quantum yield and ultrafast carrier relaxation pathways are seen to be an exciting system for quantum light emission with facile synthesis techniques.