Hole transfer dynamics between CsPbBr3 PNCs and p-phenylene diisothiocyanate

Abstract

Lead halide perovskites have rapidly emerged as promising materials for solar energy applications. A key factor in maximizing their photovoltaic efficiency is understanding the charge separation (electrons and holes) and their transfer across the interfaces. It heavily depends on the choice of electron/hole acceptors, and the search for suitable carrier acceptors is an active area of research. In this study, we report the charge transfer dynamics between cesium lead bromide (CsPbBr₃) perovskite nanocrystals (PNCs) and p-phenylene diisothiocyanate (PDNCS). The optical characteristics of the PNCs were investigated using UV-Vis absorption spectroscopy, steady-state photoluminescence (PL), and time-resolved photoluminescence spectroscopy. Femtosecond transient absorption spectroscopy (TAS), under varying excitation powers, was employed to probe charge transfer dynamics. A maximum transfer efficiency of approximately 57% was observed at an excitation energy of ∼1.39E_g (E_g = band gap). The PL quantum yield (PLQY) was found to be strongly dependent on the excitation wavelength. At a given quencher concentration, a linear increase of PLQY up to band edge excitation was observed, and a lower PLQY at high energy excitation has been explained due to higher hole transfer efficacy from PNCs to PDNCS.