Identifying the Key Issues in Inferior Performance of Quantum Rod LEDs

Quantum dot light-emitting diodes (QDLEDs) have approached the theoretical limit of external quantum efficiency (EQE) determined by outcoupling efficiency. To achieve further improvements, innovative optical designs must be explored. Quantum rod-based LEDs (QRLEDs) show great potential, offering a high transition dipole moment (TDM) orientation ratio of 80% to 90%, compared to 66.7% for isotropic QDs without complex alignment processes. However, significant performance gaps exist between QRLEDs and QDLEDs despite both types sharing similar core-shell structures and photoluminescence quantum yields (PLQY). In this paper, we identify a critical challenge: carrier leakage through irregular quantum rod films, which diminishes the EQE of QRLEDs and limits their competitiveness against QDLEDs. An equivalent circuit model consisting of two diodes effectively illustrates the impact of leakage current in conventional QDLED structures. By altering the QRLED device structure, we successfully improved balanced carrier injection while reducing the leakage current linked to the suboptimal QR layer. As a result, our QRLED achieved a maximum EQE of 30.2% (with an average of 28%) and a brightness of 110,000 cd/m². These findings will pave the way for further advancements in the performance of LEDs based on anisotropic nanocrystals.