Surface plasmon-mediated photoluminescence boost in graphene-covered CsPbBr3 quantum dots

Abstract

The optical properties of graphene (Gr)-covered CsPbBr3 quantum dots (QDs) were investigated using microphotoluminescence spectroscopy, revealing a remarkable three orders of magnitude enhancement in photoluminescence (PL) intensity compared to bare CsPbBr3 QDs. To elucidate the underlying mechanisms, we combined experimental techniques with density functional theory (DFT) calculations. DFT simulations showed that the graphene layer generates interfacial electrostatic potential barriers when in contact with the CsPbBr3 surface, impeding carrier leakage from perovskite to graphene and enhancing radiative recombination. Additionally, graphene passivates CsPbBr3 surface defect states, suppressing nonradiative recombination of photogenerated carriers. Our study also revealed that graphene becomes n-doped upon contact with CsPbBr3 QDs, activating its plasmon mode. This mode resonantly couples with photo-generated excitons in the perovskite. The momentum mismatch between graphene plasmons and free-space photons is resolved through plasmon scattering at Gr/CsPbBr3 interface corrugations, facilitating the observed super-bright emission. These findings highlight the critical role of graphene as a top contact in dramatically enhancing CsPbBr3 QDs' PL. Our work advances the understanding of graphene-perovskite interfaces and opens new avenues for designing highefficiency optoelectronic devices. The multifaceted enhancement mechanisms uncovered provide valuable insights for future research in nanophotonics and materials science, potentially leading to breakthroughs in lightemitting technologies.