Highly efficient pure red light-emitting diodes enabled by multifunctional ligand-coordinated CsPbI3 quantum dots

Efficient perovskite light-emitting diodes (PeLEDs) that emit at wavelengths between 620 and 650 nm are key to the next generation of ultrahigh-definition displays. Quantum-confined CsPbI3 quantum dots (QDs) can overcome the intrinsically narrow bandgap, thus meeting the requirements of pure red emitters. However, the inherent instability and poor carrier transport properties of CsPbI3 QDs hinder their device performance. Herein, we introduce thiophene-2-sulfonamide (2-ThSA), a short-chain multifunctional ligand, to passivate surface defects and enhance carrier transport in CsPbI3 QDs. The 2-ThSA treated QDs exhibited a near 100 % photoluminescence quantum yield (PLQY), observably improved stability, and enhanced carrier transport properties due to the strong interactions between the CsPbI3 QDs and multiple functional groups of 2-ThSA. PeLEDs based on these modified QDs demonstrated superior spectral stability, reached a remarkable external quantum efficiency (EQE) of 28.73 %, and displayed low efficiency roll-off. Additionally, large-area devices (64 mm2) showed an EQE exceeding 20 %, highlighting the potential of our approach for high-performance, large-scale displays.