Tailoring Perovskite Quantum Dot Surface Chemistry for Single Photon Emission

Abstract

Perovskite quantum dots are one of the most promising colloidal single photon sources with high single photon purity, narrow linewidths and fast radiative recombination at all temperatures. However, these materials still suffer from non-ideal behavior in the form of blinking and spectral diffusion. Both blinking and spectral diffusion are correlated to quantum dot surface quality and as such improving the surface of perovskite quantum dots is key to their long-term success as a single photon source. Here we explore the surface chemistry of perovskite quantum dots through tailoring ligand passivation and morphology. We find that CsPbBr3 quantum dots passivated with zwitterionic lecithin exhibit significantly less blinking than their oleylammonium/oleate passivated counterparts because lecithin binds to the surface ten times more strongly resulting in less ligand desorption during sample preparation. We also find that, in contrast to cubic CsPbBr3 quantum dots, spheroidal CsPbBr3 quantum dots have an asymmetric photoluminescence with a red tail due to emissive traps. Finally, we benchmark silane-based passivation for formamidinium lead bromide (FAPbBr3) quantum dots against phosphoethylammonium-based passivation for FAPbBr3 quantum dots. We find that, while silane-based passivation works extremely well at room temperature, the performance of these materials at 4K is hampered by increased trion formation which results in irreversible photodegradation.