Voltage-Controlled Reversible Modulation of Colloidal Quantum Dot Thin Film Photoluminescence

TL;DR

This paper demonstrates a voltage-controlled method to reversibly modulate colloidal quantum dot thin film photoluminescence with high contrast and fast response, combining QCSE and exciton dissociation.

Contribution

It introduces a novel device that achieves large, reversible PL modulation using electric fields, with a detailed understanding of the underlying mechanisms.

Findings

PL quenching up to 99.5% at 3 MV/cm

Contrast ratio of 200:1

Response time of 300 nanoseconds

Abstract

Active modulation of quantum dot thin film photoluminescence (PL) has far-reaching potential applications in biomedical and optoelectronic systems, but challenges remain in achieving large PL modulation depth and fast temporal response. Here we report an efficient voltage-controlled optical down-converter by optically exciting a colloidal quantum dot thin film within a quantum dot light-emitting diode (QD-LED) under reverse bias. Utilizing field-induced luminescence quenching, we show that a large electric field can strongly modify carrier dynamics in this nanostructured device, resulting in stable and reversible photoluminescence quenching. The device exhibits photoluminescence reduction of up to 99.5%, corresponding to a contrast ratio of 200:1, under the applied electric field of 3 MV/cm, with a 300 nanosecond response time. Using excitation wavelength dependent and transient PL spectroscopy, we further show that the high degree of quenching is achieved by a synergistic interplay of quantum-confined Stark effect (QCSE) and field-induced exciton dissociation.