Phosphonate-Substituted Chitosan With Complete Non-Conjugation Facilitates Efficient Hole Injection in Perovskite...

Perovskite light-emitting diodes (PeLEDs) promise efficient, pure-color next-generation displays but suffer from charge injection imbalance due to energy barriers at the indium tin oxide (ITO)/perovskite interface. To address this, we introduce non-conjugated phosphorylated chitosan (NCPC) as an efficient hole injection layer (HIL) for the first time. NCPC enhances interfacial interactions with ITO and the hole-transport layer (HTL), effectively reducing their energy barrier and achieving favorable energy level alignment. This significantly lowers both charge injection barriers and interfacial nonradiative recombination. Incorporating NCPC markedly improves device performance. Red, green, and blue PeLEDs show maximum external quantum efficiency (EQE_max) enhancements of 25.35% (670 nm), 25.45% (512 nm), and 14.22% (489 nm), respectively, compared to control devices using PEDOT:PSS HIL. Notably, the red PeLED EQE_max at 670 nm ranks among the top two reported values. The facilitated hole injection also reduces turn-on voltages. This work advances the design of efficient HILs for PeLEDs and demonstrates the potential of environmentally friendly natural materials for high-performance displays.