Ultrafast and broadband photodetectors based on a perovskite/organic bulk heterojunction for large-dynamic-range imaging

Li et al. Light: Science & Applications (2020)9:31 https://doi.org/10.1038/s41377-020-0264-5 ARTICLE Official journal of the CIOMP 2047-7538 www.nature.com/lsa Open Access Ultrafast and broadband photodetectors based on a perovskite/organic bulk heterojunction for large-dynamic-range imaging 1234567890():,; 1234567890():,; 1234567890():,; 1234567890():,; Chenglong Li1, Hailu Wang2,3, Fang Wang2,3, Tengfei Li4, Mengjian Xu2, Hao Wang2,3, Zhen Wang2,3, Xiaowei Zhan4, Weida Hu 2,3 and Liang Shen1 Abstract Organic-inorganic hybrid perovskite (OIHP) photodetectors that simultaneously achieve an ultrafast response and high sensitivity in the near-infrared (NIR) region are prerequisites for expanding current monitoring, imaging, and optical communication capbilities. Herein, we demonstrate photodetectors constructed by OIHP and an organic bulk heterojunction (BHJ) consisting of a low-bandgap nonfullerene and polymer, which achieve broadband response spectra up to 1 μm with a highest external quantum efficiency of approximately 54% at 850 nm, an ultrafast response speed of 5.6 ns and a linear dynamic range (LDR) of 191 dB. High sensitivity, ultrafast speed and a large LDR are preeminent prerequisites for the practical application of photodetectors. Encouragingly, due to the high-dynamicrange imaging capacity, high-quality visible-NIR actual imaging is achieved by employing the OIHP photodetectors. We believe that state-of-the-art OIHP photodetectors can accelerate the translation of solution-processed photodetector applications from the laboratory to the imaging market. Introduction Serving as technical functional components for the translation of optical signals into electrical signals, photodetectors have received extensive attention and have been applied in various fields, including industrial production, military affairs, biochemical detection, optical communication, and scientific research1–10. The versatility and availability of photodetectors always depend on a few predominant factors: the photoresponse speed, sensitivity to lower brightness, detection band in which photodetectors can efficaciously detect light and dynamic range Correspondence: Fang Wang () or Weida Hu () or Liang Shen () 1 State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012, China 2 State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai 200083, China Full list of author information is available at the end of the article. These author contributed equally: Chenglong Li, Hailu Wang response11–16. Correspondingly, the key photodetector parameters that are to used to evaluate these performance factors are the response time or speed, spectral responsivity (R), noise current, external quantum efficiency (EQE), specific detectivity (D*) and linear dynamic range (LDR)17–20. Recently, the exploration of high-performance photodetectors has gradually become a research focus in the field of optoelectronics and high-quality imaging. Organic-inorganic hybrid perovskites (OIHPs) are emerging materials that have been progressively enabling new thin-film optoelectronics, including solar cells21–27, light-emitting diodes28,29 and photodetectors14,16,30–36. The extensive application of hybrid perovskites can be attributable to their excellent optical and electrical properties, including a direct bandgap, large absorption coefficient, high carrier mobility, and low trap density37–40. Therefore, OIHP photodetectors have demonstrated high R, high D*, an ultrafast response speed and a high LDR when combined with device structure engineering11,18,41. However, the detection range of MAPbI3 (either © The Author(s) 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Li et al. Light: Science & Applications (2020)9:31 Page 2 of 8 polycrystalline films or thin single crystals) is limited to the wavelength region below 820 nm and does not cover the near-infrared (NIR) range, which severely limits its application, especially in biomedical imaging. To overcome this problem, an advantageous strategy has been demonstrated: combining OIHP and an organic bulk heterojunction (BHJ) consisting of donor-acceptor materials with light absorption in the NIR region16,35,36,42. Shen et al. reported a composite photodetector based on MAPbI3 and PDPPTDTPT/PCBM, which exhibited a wider detection wavelength extending to 950 nm with a 5 ns ultrafast response time16. This work provided an effective way of achieving both a wider and faster response for next-generation photodetectors. However, the sole flaw of the photodetectors was that the EQE value in the NIR region failed to reach a similar value to that in the UV-visible range, which resulted from the weak NIR absorption of the low-bandgap polymer and a mismatched energy level alignment at the interface between the OIHP and BHJ layers. Wang et al. reported photodetectors based on MAPbI3 and PDPP3T/PC71BM BHJ, achieving a slightly higher EQE of 40% in the NIR region. However, the achieved response time on the order of microseconds cannot easily meet the application requirements36. Recently, Wu et al. demonstrated a broadband photodetector with an EQE of 70% in the NIR region by coating PTB7-Th:IEICO-4F on MAPbI335. However, the photodetectors did not display an inspiring performance in terms of a lower noise current and an extremely fast response time. State-of-the-art OIHP broadband photodetectors should have a high EQE value in the NIR region, high sensitivity and an ultrafast response speed. However, no such results have been reported to date. Compared with previously reported NIR materials such as PDPPTDTPT, PDPP3T, and IEICO-4F, a fused-ring electron acceptor named F8IC with a lower bandgap and higher electron mobility has been successfully synthesized43. F8IC exhibits an extremely low b Cu BCP C 60 BHJ e vskit Pero A PTA ITO Normalized absorption (a.u.) a bandgap of 1.43 eV, which matches well with the energy levels of the polymer donor PTB7-Th (highest occupied molecular orbital (HOMO) energy level of −5.20 eV, (...truncated)