High-Brightness Transparent Quantum-Dot Light-Emitting Diodes with a Suppressed Efficiency Roll-Off

Transparent quantum-dot light-emitting diodes (Tr-QLEDs) enable information display on transparent panels, making them highly promising for next-generation applications. However, the deposition of the transparent top electrode induces defects and conductive pathways in the underlying solution-processed functional layers, disrupting charge carrier injection and transport and leading to the poor device performance. Here, we demonstrated that incorporating a nontoxic polyethylenimine-ethoxylated (PEIE) layer between the top electrode and the functional layers effectively mitigates this damage. As a result, the Tr-QLEDs achieved uniform emission from both the top and bottom sides, exhibiting an external quantum efficiency (EQE) of 17.2%, which is 1.6 times higher than that of devices without the PEIE layer. Additionally, the resultant devices demonstrated a high transmittance of over 82% at 626 nm, a current efficiency (CE) of 24.6 cd A–1, and a peak luminance of 85,120 cd m–2. Moreover, the PEIE layer suppressed excessive electron flow, improving carrier injection balance, and achieving a well-controlled efficiency roll-off at high brightness levels. The luminance at peak EQE reached approximately 20,000 cd m–2, and more than 80% of the peak EQE is maintained within a luminance range of 3000 to 60,000 cd m–2, meeting the high-brightness level requirements for outdoor display applications.