Colour-encoded electroluminescent white light-emitting diodes enabled using perovskite–Cu–In–S quantum composites

Abstract

Solution-processed quantum dot (QD) white light-emitting diodes (WLEDs) have received much attention as viable light sources in next-generation large-area ambient lighting, flexible photonics and full-colour display backlighting technologies. Attributable to their solution processibility, tunable colour temperature, high quantum efficiency and high photostability, considerable research efforts have been spent on accumulating new insights into materials and device architecture design for high-performance QD WLEDs. At present, prevalent research on WLEDs focuses on using QDs as photoluminescence colour converters or using purely narrow linewidth QD LEDs to complement the white light spectrum, which is not energy efficient as well as challenging to achieve Eye Comfort ambient colour coding. Herein, a quantum composite made by hybridising perovskite (CsPbBr₃ and CsPb(Br_1−xCl_x)₃) and CuInS₂ (CIS) QDs is proposed as a colour-encoded electroluminescent layer, which underpins good white colour temperature and bias stability for ambient lighting. Instead of using solely sharp emission QDs to match the white light spectrum, broad light emission spectrum CIS QDs are used for colour temperature tuning. In addition, the mixed-halide perovskite CsPb(Br_1−xCl_x)₃ QDs are successfully synthesised through a noninvasive halide ion exchange method associated with trimethylsilyl chloride additives, which provide a good colour purity in the blue and green electroluminescence regions. These designed QD composites enable the as-prepared WLED electroluminescence spectra to match the ideal ambient light Commission International de l’Éclairage 1931 (CIE) colour coordinates with a mean value of 0.33, 0.34. Moreover, the as-prepared WLEDs show a turn-on voltage of 4 V with negligibly small leakage current, good colour stability and electrical bias tolerance even under a broad range of driving voltages. Our results herald the advent of molecular level hybridisation of different quantum materials for high-performance electroluminescence white colour toning.