Strongly Bonded Organic Acids Passivate Perovskite Quantum Dot Surfaces to Achieve High Brightness and Stability

The engineering of surficial ligands plays a crucial role in the optoelectronic performance of perovskite quantum dot light-emitting diodes (PQD-LEDs). In this work, via a ligand exchange strategy using diisooctylphosphinic acid (DOPA), which exhibits stronger bonding capacity with component Pb²⁺ ions, the surface ligands of FA_0.15Cs_0.85PbBr₃ PQDs are optimized, beneficial for both radiative recombination and operational stability. The green PQD-LED (peaking at 520 nm) achieves a maximum luminance of 1.337 × 10⁵ cd m^-2, with an external excitation efficiency of 16.88%, and a long operational lifetime (T₅₀) of 4.31 h at a high luminous of 1000 cd m^-2. The restriction of Br^- ion migration in PQDs, by using DOPA ligands to alter the surficial species and lattice components, results in stable emission peaks that are independent of bias voltage and operation time. This method is widely applicable for fabricating optoelectronic devices using PQDs with mixed components to improve efficiency and stability.