Tunable Green-to-Blue Light Emitting Hybrid Perovskite Nanocrystals: Status Updates and Roadblocks

Perovskite nanocrystals (NCs) have demonstrated tremendous success in the field of optoelectronics due to their exceptional optical properties. Their high photoluminescence quantum yield (PLQY), tunable emission, defect tolerance, and facile synthesis make them ideal candidates for application in light-emitting diodes (LED). While the external quantum efficiency (EQE) of green and red perovskite-based LEDs (PeLEDs) has exceeded 20%, which is on par with organic- and quantum dot-based LEDs, blue PeLEDs still lag behind their counterparts. This review focuses on the evolution of obtaining highly efficient, tunable green-to-blue emitting methylammonium lead bromide (MAPbBr3) perovskite NCs by optimizing their optoelectronic properties. In detail, we first review the strategies for synthesizing and fine-tuning their emission spectra (450-520 nm), followed by a discussion on the key issues for achieving highly stable blue-emitting NCs and how to overcome these issues. The pros and cons of ligand engineering, metal doping, core-shell structure formation, and postsynthetic treatments are discussed. This Review also covers the progress in the fabrication of blue- and green-emitting PeLEDs, including device architecture optimization for maximizing the light out-coupling efficiency. Finally, the remaining challenges and future opportunities for blue-emitting MA-based PeLEDs are outlined.