Shi Linlin, Zhu Yizhi, Li Guohui, Ji Ting, Wang Wenyan, Zhang Ye, Wu Yukun, Hao Yuying, Wang Kaiying, Yuan Jun, Zou Yingping, Ong Beng S, Zhu Furong, Cui Yanxia
College of Optoelectronics, Key Laboratory of Interface Science and Engineering in Advanced Materials, Key Laboratory of Advanced Transducers and Intelligent Control System of Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China.
College of Optoelectronics, Key Laboratory of Interface Science and Engineering in Advanced Materials, Key Laboratory of Advanced Transducers and Intelligent Control System of Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China; College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
Sci Bull (Beijing). 2023 May 15;68(9):928-937. doi: 10.1016/j.scib.2023.04.015. Epub 2023 Apr 13.
Low-cost, solution-processed photomultiplication organic photodetectors (PM-OPDs) with external quantum efficiency (EQE) above unity have attracted enormous attention. However, their weak-light detection is unpleasant because the anode Ohmic contact causes exacerbation in dark current. Here, we introduce atomic-level chemical reaction in PM-OPDs which can simultaneously suppress dark current and increase EQE via depositing a 0.8 nm thick AlO by the atomic layer deposition. Suppression in dark current mainly originates from the built-in anode Schottky junction as a result of work function decrease of hole-transporting layer of which the chemical groups can react chemically with the bottom surface of AlO layer at the atomic-level. Such strategy of suppressing dark current is not adverse to charge injection under illumination; instead, responsivity enhancement is realized because charge injection can shift from cathode to anode, of which the neighborhood possesses increased photogenerated carriers. Consequently, weak-light detection limit of the forwardly-biased PM-OPD with AlO treatment reaches a remarkable level of 2.5 nW cm, while that of the reversely-biased control is 25 times inferior. Meanwhile, the PM-OPD yields a record high EQE and responsivity of 4.31 × 10% and 1.85 × 10 A W, respectively, outperforming all other polymer-based PM-OPDs.
具有高于单位外量子效率（EQE）的低成本、溶液处理的光电倍增有机光电探测器（PM-OPD）引起了广泛关注。然而，它们的弱光检测效果不佳，因为阳极欧姆接触会导致暗电流加剧。在这里，我们在PM-OPD中引入原子级化学反应，通过原子层沉积沉积0.8纳米厚的AlO，可以同时抑制暗电流并提高EQE。暗电流的抑制主要源于内置阳极肖特基结，这是由于空穴传输层的功函数降低，其化学基团可以在原子水平上与AlO层的底面发生化学反应。这种抑制暗电流的策略在光照下对电荷注入没有不利影响；相反，由于电荷注入可以从阴极转移到阳极，而阳极附近有更多的光生载流子，因此实现了响应度的提高。因此，经过AlO处理的正向偏置PM-OPD的弱光检测极限达到了2.5 nW cm的显著水平，而反向偏置对照的弱光检测极限则差25倍。同时，该PM-OPD分别产生了创纪录的高EQE和响应度，分别为4.31×10%和1.85×10 A W，优于所有其他基于聚合物的PM-OPD。
