Department of Electrical and Electronic Engineering, Southern University of Science and Technology , Shenzhen 518055, P. R. China.
State Key Lab of Optoelectronic Materials and Technologies, School of Materials Science and Engineering, Sun Yat-sen University , Guangzhou 510275, P. R. China.
ACS Appl Mater Interfaces. 2016 Jul 6;8(26):16768-75. doi: 10.1021/acsami.6b03367. Epub 2016 Jun 24.
The microcavity effect in top-emitting quantum dot light-emitting diodes (TQLEDs) is theoretically and experimentally investigated. By carefully optimizing the cavity length, the thickness of the top Ag electrode and the thickness of the capping layer, very bright and efficient TQLEDs with external quantum efficiency (EQE) of 12.5% are demonstrated. Strong dependence of luminance and efficiency on cavity length is observed, in good agreement with theoretical calculation. By setting the normal-direction resonant wavelength around the peak wavelength of the intrinsic emission, highest luminance of 112 000 cd/m(2) (at a driving voltage of 7 V) and maximum current efficiency of 27.8 cd/A are achieved, representing a 12-fold and a 2.1-fold enhancement compared to 9000 cd/m(2) and 13.2 cd/A of the conventional bottom emitting devices, respectively, whereas the highest EQE of 12.5% is obtained by setting the resonant wavelength 30 nm longer than the peak wavelength of the intrinsic emission. Benefit from the very narrow spectrum of QDs and the low absorption of silver electrodes, the potential of microcavity effect can be fully exploited in TQLEDs.
本文理论和实验研究了顶发射量子点发光二极管（TQLED）中的微腔效应。通过仔细优化腔长、顶 Ag 电极的厚度和覆盖层的厚度，成功制备出具有 12.5%外量子效率（EQE）的非常明亮和高效的 TQLED。观察到亮度和效率对腔长的强烈依赖性，与理论计算吻合较好。通过将法向共振波长设置在本征发射峰的峰值波长附近，实现了 112000 cd/m²（在 7 V 的驱动电压下）的最高亮度和 27.8 cd/A 的最大电流效率，分别比传统底发射器件的 9000 cd/m²和 13.2 cd/A 提高了 12 倍和 2.1 倍，而将共振波长设置为比本征发射峰的峰值波长长 30nm 时，则可获得 12.5%的最高 EQE。得益于量子点的非常窄的光谱和银电极的低吸收率，TQLED 中的微腔效应的潜力可以得到充分利用。
