Quantifying the Electrical Excitation Level of Quantum Dots for Mitigating Electroluminescent Efficiency Roll-Off

Understanding the electrical excitation level of quantum dots in light-emitting diodes (LEDs) constitutes a central aspect of investigations into device mechanisms. However, practical research is hindered by the absence of straightforward and viable analytical methodologies. In this study, we present an approach for assessing device quality by examining the electrical excitation level of quantum dots in conjunction with carrier injection balance. Through quantitative modeling of electroluminescent intensity and the average number of excitons () generated under electrical excitation, key parameters that manifest the current utilization efficiency can be extracted, providing a guideline to inform device optimization strategies. As a proof of concept, the efficiency roll-off of blue-emitting perovskite quantum dot LEDs is theoretically analyzed. Combining electrically excited transient absorption spectroscopy, hole leakage is identified as the main cause of low current utilization efficiency. Mitigating carrier injection imbalance via enhancing electron injection, the blue device simultaneously achieves a high brightness of over 11 000 cd m^-2 and a maximum EQE of 26.0%, representing state-of-the-art blue perovskite LEDs.