Single-component electroluminescent white light-emitting diodes based on zinc oxide quantum dots with high color rendition and tunable correlated color temperature

Single-component white light-emitting diodes (WLEDs) with high color rendition and adjustable correlated color temperature (CCT) are crucial to meet various lighting needs. Unfortunately, the development of efficient electroluminescent single-component WLEDs remains a challenge because of the issue of Kasha's rule. This work report the first demonstration of single-component electroluminescent WLEDs with widely adjustable CCT from 3303 to 8055 K and a very high color rendering index (>90) by using the zinc oxide quantum dots (ZnO-QDs), synthesized via a low temperature sol-gel method, as emissive layers. It is found that the electroluminescence intensity of different wavebands of the ZnO-QDs-based single-component WLEDs (ZnO-WLEDs) can be modulated effectively by the regulation of recombination centers and rates through hole transport layer (HTL) engineering. As a result, a series of warm to cold ZnO-WLEDs are realized with an ultralow turn-on voltage of 2.0 V, the maximum luminance up to 1214 cd m⁻², and excellent color chromatic stability by the doping of poly(9,9-dioctylfluorene-co-N-(4-(3-methylpropyl)) diphenylamine) into HTLs, which are among the best performance of single-component ZnO-WLEDs. These results are very encouraging, and open up a new avenue for the development of low-cost, environment-friendly, and high-performance single-component WLEDs.