Efficient CsPbBr3 Nanoplatelet-Based Blue Light-Emitting Diodes Enabled by Engineered Surface Ligands

Quantum-confined CsPbBr3 nanoplatelets (NPLs) with very narrow emission line width are promising candidates for color-saturated blue emitters, but their electroluminescence performance is limited by inferior carrier transport, mostly induced by the surface bulky organic ligands. Many efforts routinely rely on replacing long ligands with short counterparts, resulting in a significant increase in the NPL's thickness and thus making it difficult to obtain the desired emission color. Herein, we realize short-ligand (butylamine and myristic acid)-capped CsPbBr3 NPLs with almost unaltered emission characteristics by introducing ammonium bromide (NH4Br) to effectively control the crystal growth kinetics and passivate the surface defects. Further, with short conjugation ligand–phenethylammonium bromide (PEABr) postsynthetic treatment, we can dramatically enhance their electrical performance and luminous efficiency (film photoluminescence quantum yields over 80%). With these benefits, a remarkable electroluminescence efficiency of 2% (at 463 nm) has been achieved, which is a record for blue perovskite NPL-based light-emitting diodes.