Xingzhi Wang,Jiahui Sun,Rui Guo,Zhijie Yan,Bo Li,Lei Wang,Huaibin Shen,Fengjia Fan
The electric field-induced quantum confined Stark effect is an important factor that can affect the performance of quantum dot light-emitting diodes. However, probing this Stark effect in the operating quantum dot light-emitting diodes is still experimentally challenging using available characterization techniques. Herein we combine our self-developed electrically excited transient absorption spectroscopy with theoretical simulation to unveil the complex size dependence of the Stark effect in quantum dot light-emitting diodes. We found that the Stark effect-induced exciton quenching depends on both wave function confinement and the screening effect. Under reversed biases, the Stark–voltage relationship reveals that smaller quantum dots are less electric field-sensitive because of stronger wave function confinement; while under forward biases, larger quantum dots exhibit stronger electric-field screening and smaller equivalent bias because of more efficient carrier injection─with these intertwined factors, we observed the strongest electric field-induced exciton quenching in medium-size quantum dots.
Ai Yansong,He Hongshen,Shen Peng,Wang Zhenyang,Zhang Hui,Zhou Yuanming,Mei Fei
Perovskite light-emitting diodes (PeLEDs) have attracted considerable attention in optoelectronic devices due to their excellent performance. Here, the performance of PeLEDs was improved by utilizing l -phenylalanine-doped PEDOT:PSS as hole transport layer (HTL). The optimal device with l -phenylalanine doped HTL shows a maximum luminance of 3800 cd/m 2 and a maximum external quantum efficiency of 2.80%. Compared with the control device using pure PEDOT:PSS HTL, the maximum luminance was increased by 90%, and the maximum external quantum efficiency was increased by 154%, respectively. This is mainly due to the fact that PEDOT:PSS with l -phenylalanine doping optimizes the morphology of the perovskite film and suppresses the exciton quenching at the HTL/perovskite interface. In addition, moderate addition of l -phenylalanine can enhance the hole injection capability of HTL. These experimental results provide proof of amino acid-modified PEDOT:PSS as HTL and a basis for improving the performance of PeLEDs.
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