Entropic-Ligand-Driven Efficient and Stable CsPbI(3) Quantum Dot Light-Emitting Diodes.

Colloidal perovskite quantum dots (QDs) show great promise for next-generation optoelectronics. However, their performance in solid films is significantly limited by ligand interdigitation, which quenches luminescence and compromises stability. Here, we develop an entropic ligand strategy employing branched alkylamines that fundamentally re-engineers the surface chemistry of CsPbI QDs. We report enhanced optoelectronic properties in QD solids achieved by ligand tail engineering. This approach tailors ligand configurational entropy and adsorption energy, suppressing deleterious interdigitation and promoting ordered superlattice assembly. The modified QDs exhibit markedly improved emission efficiency, achieving near-unity quantum yield in solution (up from 78%) and 81% in solid films (up from 31%). When deployed in light-emitting diodes, these benefits yield a peak external quantum efficiency of 27.09%, an 11-fold improvement in operational lifetime, and substantially reduced efficiency roll-off. This work establishes entropic ligand design as a robust pathway to enhance brightness, stability, and charge transport.