Ratio-induced competition between energy and charge transfer in InP/ZnS quantum dots: A color-converting and high-performance LED

Abstract

Understanding how semiconductor quantum dots (QDs) participate in photoinduced fluorescence resonance energy transfer (FRET) and charge transfer (CT) is essential for enhancing the performance of light-emitting diodes (LEDs). Herein, steady-state emission and ultrafast transient absorption spectroscopy measurements demonstrate that the FRET and CT processes occur from green-emitting InP/ZnS QDs (as donor) to yellow-emitting InP/ZnS QDs (as acceptor). With an increase in the proportion of donor QDs, the fluorescence quenching pathway gradually shifts from being predominantly governed by FRET interaction (∼82% FRET, ∼18% CT) to being dominated by CT interaction (∼23% FRET, ∼77% CT). Detailed photophysical analysis reveals a competitive relationship between CT and FRET in the binary mixture of these two InP/ZnS QDs, which is associated with the underlying spectral overlap and the influence of donor–acceptor distance. Importantly, the enhanced CT process and suppressed FRET process in the InP/ZnS QDs system effectively promote the color conversion, brightness, and external quantum efficiency of the LEDs. These findings will open up a paradigm for improving the color and efficiency of optoelectronic devices based on QDs.