Acta Chimica Sinica ›› 2021, Vol. 79 ›› Issue (8): 1030-1036.DOI: 10.6023/A21040181 Previous Articles     Next Articles



王成a,b, 张弛a, 陈琪a,c,*(), 陈立桅a,d   

  1. a 中国科学院苏州纳米技术与纳米仿生研究所 中国科学院纳米科学卓越中心 国际实验室 苏州 215123
    b 上海科技大学 物质科学与技术学院 上海 201210
    c 中国科学技术大学 纳米技术与纳米仿生学院 合肥 230026
    d 上海交通大学 化学与化工学院 物质科学原位中心 上海 200240
  • 投稿日期:2021-04-27 发布日期:2021-05-20
  • 通讯作者: 陈琪
  • 基金资助:
    国家重点研究发展计划(2016YFA0200700); 国家自然科学基金(21625304); 国家自然科学基金(21875280); 国家自然科学基金(22022205); 国家自然科学基金(21991150); 国家自然科学基金(21991153)

Improving the Photomultiplication in Organic Photodetectors with Narrowband Response by Interfacial Engineering

Cheng Wanga,b, Chi Zhanga, Qi Chena,c(), Liwei Chena,d   

  1. a i-Lab, CAS Center for Excellence in Nanoscience, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
    b School of Physical Science and Technology, Shanghai Tech University, Shanghai 201210, China
    c School of Nano-Tech and Nano-Bionics, University of Science and Technology of China, Hefei 230026, China
    d In-situ Center for Physical Sciences, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
  • Received:2021-04-27 Published:2021-05-20
  • Contact: Qi Chen
  • Supported by:
    Ministry of Science and Technology of China(2016YFA0200700); National Natural Science Foundation of China(21625304); National Natural Science Foundation of China(21875280); National Natural Science Foundation of China(22022205); National Natural Science Foundation of China(21991150); National Natural Science Foundation of China(21991153)

Narrow-band response photodetectors are widely used in situations where specific light wavelengths need to be detected, such as communication, imaging, surveillance, etc. These detectors require not only the narrowest spectral response window, but also the highest external quantum efficiency (EQE) within the response window. Generally, the semiconductor photoactive layer in the photodetector will absorb the photons with energy greater than the band gap, and the spectral response window is usually wide, so it needs to combine with the filter of specific wavelength to achieve narrow band response. However, the introduction of filters, in addition to the increased cost, will inevitably lead to additional light reflection losses, which will significantly reduce EQE. When the film thickness of the heterojunction is up to μm, the narrow-band response near the band edge can be achieved without a filter. However, the problem brought by thick film is that the photocurrent also decreases, resulting in lower EQE (<30%) of the device. Although higher reverse bias increases the photocurrent and EQE, it also increases the collection probability of short-wave photogenerated carriers, thus damaging the narrow-band response. By greatly reducing the proportion of organic receptors and donors in the micron-size photoactive layer, the narrow-band response window of ca. 650 nm was achieved, and the EQE was up to ca. 53500% under –60 V reverse bias. This kind of organic photodetector achieving the photomultiplication mainly attributes to the trapped charges at the photoactive layer/electrode interface which will capture the photogenerated electrons (holes), and when the photogenerated electrons (holes) are collected, the electric neutral balance in the photoactive layer is broken. The trapped photogenerated electrons (holes) at the interface will cause the change of interface potential energy, which induces the interface band bending of the photoactive layer, and promotes the metal electrode to inject holes into the photoactive layer to maintain the neutral balance. Because the injection current is much higher than the photoelectric current, the superposition of the two can significantly increase EQE and even produce gain. However, the idea of obtaining higher EQE by further increasing the concentration of interfacial trapped electrons is difficult to be realized by increasing the proportion of receptors, which not only reduces EQE, but also increases the full width at half maximum (FWHM) of the response window and destroys the narrow-band response. In this work, the structure of ITO/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT)/poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61-isomethyl butyrate (PCBM)/aluminum (Al) has been prepared. By optimizing the thermal anneal-ing time and PCBM concentration, the EQE at –60 V was successfully improved from 52946.8% to 68470.9%, which is the highest gain of narrow-band response organic photodetector so far, and the FWHM of ca. 28 nm remains unchanged. We used Nano-IR to confirm that EQE enhancement was attributed to thermal annealing induced diffusion of PCBM into P3HT, thus optimizing the electron trap concentration distribution at the interface between the active layer and the metal top electrode and enhancing carrier injection.

Key words: organic photodetector, photomultiplication, narrow-band response, thermal annealing, interfacial engineering, Nano-IR