Synergistic Effect of Ligands and Halogen Vacancies for Pure-Red CsPbI₃ Superlattice Light-Emitting Diodes

CsPbI3 nanocrystals (NCs) are ideal for the next generation of pure red light-emitting diodes (LEDs). However, the increased surface defects in NCs cause severe nonradiative recombination, thereby worsening their electroluminescence performance. Herein, by modulating the adsorption energy of tetrabutylammonium iodide (TBAI) ligand on different surfaces of CsPbI3 NCs to achieve selective desorption of the ligand on the surfaces, we exploited the synergistic effect of the TBAI ligand and halogen vacancies to self-assemble CsPbI3 NCs into nanocubic superlattices. LEDs fabricated based on the superlattice structure achieved a maximum external quantum efficiency (EQE) of 15.72% and a maximum luminance of 6149 cd/m2, which is the first report on pure-red-light LEDs (630–650 nm range) based on CsPbI3 superlattices. At a luminance of 1007 cd/m2, the devices maintained an EQE of over 13%, with a T50 improved by approximately 2.5 times.