Binary Host‐induced Exciplex Enabled High Color‐Rendering Index of 94 for Carbon Quantum Dot‐Based White Light‐Emitting Diodes

Abstract

Abstract White light‐emitting diodes (WLEDs) with high color‐rendering index (CRI, >90) are important for backlight displays and solid‐state lighting applications. Although the well‐developed colloidal quantum dots (QDs) based on heavy metals such as cadmium and lead are promising candidates for WLEDs, the low CRI still remains a significant limitation. In addition, the severe toxicity of heavy metals greatly limits their widespread use. Herein, the study demonstrates low‐cost and environmentally friendly carbon quantum dots (CQDs)‐based WLEDs that exhibit a high CRI of 94.33, surpassing that of conventional cadmium/lead‐containing QD‐based WLEDs. This achievement is attained through the employment of a binary host‐induced exciplex strategy. The high hole/electron mobility and suitable energy levels of the donor and acceptor give rise to a broadband orange–yellow emission stemming from the exciplex. As the host, the binary exciplex is capable of contributing blue and orange–yellow emission components while efficiently mitigating the aggregation‐induced quenching of CQDs. Meanwhile, CQDs effectively address the deep‐red emission gap, enabling the realization of CQDs‐based WLEDs with high CRI. These WLEDs also exhibit a remarkably low turn‐on voltage of 2.8 V, a maximum luminance exceeding 2000 cd m−2, a correlated color temperature of 4976 K, and Commission Internationale de l'Eclairage coordinates of (0.34, 0.32).

Keywords

• binary host‐induced exciplex
• carbon quantum dots
• color rendering index
• white light‐emitting diodes