Exploring Orbit-Orbit Interaction in Relationship with Photoluminescence Quantum Efficiency in Perovskite Quantum Dots through Rashba Effects.

Abstract

Metal halide perovskite quantum dots attract significant research interest in recent years due to their exceptional optical properties, such as tunable emission wavelength, strong quantum confinement and suppressed non-radiative recombination via surface passivation. However, the presence of dark states with low emission rate in perovskite quantum dots due to the strong spin-orbital coupling (SOC) and Rashba effects may suppress light emission efficiency. Strategies of reducing bright-to-dark exciton conversion through spin-orbital coupling (SOC) has been rarely addressed. In this work, we fabricated CsPbBr1I2 quantum dots with controlled size and uniformity by using different capping ligands. The orbit-orbit interactions between photogenerated excitons in CsPbBr1I2 quantum dots are studied based on photoexcitation polarization dependent photoluminescence. Decreasing orbit-orbit interaction in CsPbBr1I2 quantum dots can result in an improved photoluminescence quantum efficiency, which implies that less populated dark excitons with indirect recombination are generated through weak spin flipping. The PL lifetime results confirm that the improved light emission efficiency by changing organic ligand is mainly induced by tuning Rashba effects in quantum dots rather than trap passivation. These findings provide new insight on tuning Rashba effects in perovskite quantum dots towards enhanced light emission efficiency via surface modification.