Geometry-dependent self-heating and wall-plug efficiency degradation in RGB quantum dot LEDs probed by thermoreflectance microscopy

초록

Quantum dot light-emitting diodes (QD-LEDs) have emerged as promising candidates for next-generation display applications. However, their electrical, optical, and thermal characteristics depend on the intrinsic properties of quantum dots and device geometry. In this study, we investigate the self-heating effect (SHE) of QD-LEDs with different pixel areas (100 & times; 100, 150 & times; 150, and 200 & times; 200 mu m(2)). We utilize thermoreflectance microscopy (TRM) to analyze temperature characteristics under pulsed voltage electrical operation. This facilitates the evaluation of geometry-dependent heat generation and dissipation. We explain how pixel area variation affects temperature change (Delta T), thermal nonuniformity, and wall-plug efficiency (WPE) by correlating thermal responses derived from TRM measurement with electrical and optical characteristics. Delta T of approximately 1.4-13 degrees C was measured depending on device pixel areas and this Joule heating was correlated with WPE degradation. The WPE decreased by approximately 78%-99%, with larger-pixel devices exhibiting stronger heat accumulation, more pronounced thermal nonuniformity, and greater efficiency loss than smaller pixel devices. These findings indicate that the SHE is a pivotal factor in governing electro-thermal reliability and optical characteristics of QD-LEDs. This work provides insight into thermal related reliability issues in QD-LEDs for next-generation display applications.