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

## TL;DR

This paper introduces a high-efficiency hole injection layer made from reduced graphene oxide that significantly improves the performance of quantum dot light-emitting diodes.

## Contribution

The novel contribution is the thermal reduction of graphene oxide at 160°C to create an efficient hole injection layer for QLEDs.

## Key findings

- Thermally reduced graphene oxide boosts current density by two orders of magnitude and lowers hole injection barriers.
- rGO-based QLEDs achieve a peak external quantum efficiency of 13.31% and current efficiency of 14.93 cd A−1.
- rGO-based devices show superior thermal stability and low-temperature operability compared to GO-based devices.

## Abstract

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.

rGO-based QLEDs achieve excellent performance (2.0 V turn-on voltage, 120 000 cd m−2 maximum luminance, 11.74%EQE), on par with same-batch PEDOT:PSS-based devices.