Ultrabright, Efficient, and Stable Green Quantum Dot Light‐Emitting Diodes Through Effective Heat Dissipation

ABSTRACT Heat generation induced by electrical driving is primarily responsible for the device failure in quantum dot light‐emitting diodes (QD‐LEDs). Elucidating the thermally induced degeneration mechanism is crucial to enhancing operational lifetime and luminescent efficiency of the devices. Heightening heat dissipation can mitigate device degradation by utilizing high thermal conductivity materials, allowing for ultrahigh luminance and enhanced efficiency at high driving voltages. Here we constructively propose an underlying mechanism by which heat accumulation within the device enhances carrier delocalization in QDs, and induces the accumulation of numerous holes and electrons in non‐recombination regions, which reduce the charge density available for recombination, resulting in restricted peak brightness and device failure. On this basis, a universally feasible encapsulation strategy is developed to accelerate heat dissipation, enabling record‐breaking green QD‐LEDs with a luminance of 2 036 000 cd m −2 , an external quantum efficiency of 32.1%, and a T 95 operation lifetime (time for the luminance decreasing by 95%) of more than 32 000 h at 1000 cd m −2 .