Interfacially Weakened Förster Resonance Energy Transfer of Biocompatible Hole Transport Layers for Enhanced Perovskite Light‐Emitting Diodes

Abstract The green, low‐cost, and biocompatible organic semiconductor chlorophyll (Chl) is an ideal alternative hole transport layer of perovskite light‐emitting diodes (PeLEDs). However, the excessive electrostatic interaction between the chlorophyll molecules and the perovskite luminescent layer can severely lead to a Förster resonance energy transfer (FRET) phenomenon at the interface and greatly reduce the performance of PeLEDs. Here, sodium copper chlorophyllin (NaCu‐Chl) with a unique “single‐point configuration” of negative electrostatic potential distribution is theoretically designed to effectively weaken the interfacial electrostatic anchoring effect and successfully suppress the interfacial FRET. Experimentally, its weaker interfacial FRET is proved to result in a stronger photoluminescence (PL) at 528 nm as well as a longer exciton lifetime. Furthermore, its more matched energy levels with perovskite can lead to a smaller hole injection barrier, effectively reducing nonradiative recombination. As a result, the NaCu‐Chl‐based PeLEDs device exhibits a higher external quantum efficiency (EQE) of 7.53%, 5.75 times luminance (65024 cd m −2 ), and 4.27 times half lifetime ( T 50 ) compared to Chl‐based PeLEDs. Evidently, this work provides a strategy to effectively suppress intrinsically strong FRET at the chlorophyll/perovskite interface for efficient PeLEDs and promotes the promising application of green, low‐cost, and biocompatible chlorophyll hole transport layer (HTL) in PeLEDs.