Comparative Study of Two Different Quasi-Type II Heterostructured Quantum Dots for Enhanced Electroluminescence

Enhancing the performance of quantum dot light-emitting diodes (QD-LEDs) often involves using wide band gap shells to confine charge carriers, which has proven to be an effective strategy. However, injecting charges within the core is critical to device efficiency, and controlling heterostructures can provide deeper insights into charge dynamics. In this study, we independently manipulated electron and hole injection while maintaining consistent emission properties by using the same core but growing distinct shells. Two types of quasi-type II QDs were synthesized: acceptor QDs (A-QD) for hole injection and donor QDs (D-QD) for electron injection. By varying the deposition order of these QDs, we observed significant differences in charge injection efficiencies that strongly influenced device performance. Notably, the combination of A-QDs near the hole transport layer and D-QDs near the electron transport layer (AD-QD-LED) resulted in a maximum brightness of 81,400 cd/m2 and an efficiency of 9.1 cd/A, representing nearly 30 times higher luminance and 15 times greater efficiency compared to the DA-QD-LED. Our findings provide the first clear demonstration of how the combination of quasi-type II QDs with tailored core/shell structures can control charge injection dynamics in QD-LEDs, offering a new pathway for optimizing charge balance and enhancing device efficiency.