Advances, Challenges, and Perspectives for Heavy-Metal-Free Blue-Emitting Indium Phosphide Quantum Dot Light-Emitting Diodes

Quantum dot light-emitting diodes (QLEDs), regarded as promising candidates in the next-generation display, have attracted much attention recently. In spite of the outstanding performance of cadmium-based (Cd-based) QLEDs, the toxicity of Cd hinders their wide application. Indium phosphide quantum dots (InP QDs) with heavy-metal-free feature and competitive performance are considered to be able to replace Cd-based QDs as emitting layer in the QLEDs. Much progress is obtained in the red-emitting and green-emitting InP-based QLEDs. However, the blue-emitting ones are faced with great challenges and are demanded on full-color display urgently, which is limited by the inferior performance of blue-emitting InP QDs and lack of investigations about their QLED devices. In this review, the encountered challenges for high-quality blue-emitting InP QDs are presented. Common strategies for blue-emitting InP QDs, including size engineering, composition engineering, and surface engineering are presented and analyzed. The progress of blue-emitting InP-based QLEDs, which strongly relies on the advances of materials, is also summarized. Finally, some perspectives from device physics are provided and discussed to inspire more efficient strategies toward blue-emitting InP-based QLEDs.