Mixed-halide bromine-iodine perovskite quantum dots (PeQDs) offer excellent spectral tunability for red PeLEDs, but surface defects promote halide migration and non-radiative recombination, reducing performance. To address this issue, a Ningbo University research team has developed an innovative post-treatment strategy employing pseudohalogen inorganic ligands in acetonitrile to simultaneously etch lead-rich surfaces and passivate defects in-situ.
This method produces high-quality CsPb(Br/I)3 PeQDs with suppressed halide migration, enhanced photoluminescence quantum yield (PLQY), and improved film conductivity.
The post-treatment strategy uses short, strongly binding inorganic ligands (potassium thiocyanate (KSCN) and guanidinium thiocyanate (GASCN)) in acetonitrile to simultaneously etch lead-rich surfaces and passivate defects in CsPb(Br/I)3 PeQDs. Acetonitrile gently removes lead defects through strong Pb²⁺ coordination while preserving QD integrity, unlike polar solvents such as DMSO or DMF, which can damage PeQDs. KSCN and GASCN adsorb robustly to passivate uncoordinated Pb²⁺ sites, yielding high-quality PeQDs with enhanced PLQY, improved stability, and superior film conductivity.
Consequently, the team's spectrally stable champion PeLEDs achieved a peak external quantum efficiency (EQE) of 22.1%, one of the highest reported for mixed-halide CsPb(Br/I)3 PeQDs, representing a significant advancement in perovskite optoelectronics.
