Two-dimensional reduced graphene oxide as high-efficiency hole injection layer for quantum dot light-emitting diodes

Carrier injection imbalance severely limits the performance of quantum dot light-emitting diodes (QLEDs), emphasizing the demand for advanced transport layer materials. Herein, a high-performance reduced graphene oxide (rGO) hole injection layer (HIL) is prepared by thermally treating graphene oxide (GO) at 160 °C for 30 min, which boosts current density by two orders of magnitude, and tunes work function to 5.04 eV, thus lowering hole injection barriers. rGO-based QLEDs exhibit excellent optoelectronic performance, featuring a 2.0 V turn-on voltage and a maximum luminance of 120 000 cd m^-2. Their peak external quantum efficiency (EQE) and current efficiency are enhanced from 8.07% and 8.99 cd A^-1 (for same-batch GO-based devices) to 11.51% and 12.65 cd A^-1. Further optimization elevates their peak EQE and current efficiency (CE) to 13.31% and 14.93 cd A^-1, respectively. Performance gains stem from enhanced rGO conductivity, with rGO-based devices boasting superior thermal stability and low-temperature operability. This study verifies thermally reduced rGO as an ideal high-performance HIL, offering a new possibility for QLED optimization.