Pan Yuzhu, Wang Xin, Xu Yubing, Li Yuwei, Elemike Elias Emeka, Shuja Ahmed, Li Qing, Zhang Xiaobing, Chen Jing, Zhao Zhiwei, Lei Wei
School of Electronic Science and Engineering, Joint International Research Laboratory of Information Display and Visualization, Southeast University, Nanjing, China.
Chemistry Department of North West University, Mafikeng, South Africa.
Front Chem. 2020 Sep 10;8:791. doi: 10.3389/fchem.2020.00791. eCollection 2020.
Introducing hole/electron transporting and blocking layers is considered to enhance the performance of electronic devices based on organic-inorganic hybrid halide perovskite single crystals (PSCs). In many photodiodes, the hole/electron transporting or blocking materials are spin-coated or thermal-evaporated on PSC to fabricate heterojunctions. However, the heterojunction interfaces due to lattice mismatch between hole/electron, transporting or blocking materials and perovskites easily form traps and cracks, which cause noise and leakage current. Besides, these low-mobility transporting layers increase the difficulty of transporting carriers generated by photons to the electrode; hence, they also increase the response time for photo detection. In the present study, MAPbCl-MAPbBrCl heterojunction interfaces were realized by liquid-phase epitaxy, in which MAPbBrCl PSC acts as an active layer and MAPbCl PSC acts as a hole blocking layer (HBL). Our PIN photodiodes with epitaxial MAPbCl PSC as HBL show better performance in dark current, light responsivity, stability, and response time than the photodiodes with spin-coated organic PCBM as HBL. These results suggest that the heterojunction interface formed between two bulk PSCs with different halide compositions by epitaxy growth is very useful for effectively blocking the injected charges under high external electric field, which could improve the collection of photo-generated carriers and hereby enhance the detection performance of the photodiode. Furthermore, the PIN photodiodes made of PSC with epitaxial HBL show the sensitivities of 7.08 mC Gy cm, 4.04 mC Gy cm, and 2.38 mC Gy cm for 40-keV, 60-keV, and 80-keV X-ray, respectively.
引入空穴/电子传输和阻挡层被认为可以提高基于有机-无机杂化卤化物钙钛矿单晶（PSC）的电子器件的性能。在许多光电二极管中，空穴/电子传输或阻挡材料通过旋涂或热蒸发沉积在PSC上以制造异质结。然而，由于空穴/电子传输或阻挡材料与钙钛矿之间的晶格失配，异质结界面容易形成陷阱和裂纹，从而导致噪声和漏电流。此外，这些低迁移率的传输层增加了将光子产生的载流子传输到电极的难度；因此，它们也增加了光检测的响应时间。在本研究中，通过液相外延实现了MAPbCl-MAPbBrCl异质结界面，其中MAPbBrCl PSC作为有源层，MAPbCl PSC作为空穴阻挡层（HBL）。我们的以外延MAPbCl PSC作为HBL的PIN光电二极管在暗电流、光响应度、稳定性和响应时间方面比以旋涂有机PCBM作为HBL的光电二极管表现出更好的性能。这些结果表明，通过外延生长在两种具有不同卤化物组成的块状PSC之间形成的异质结界面对于在高外部电场下有效阻挡注入电荷非常有用，这可以改善光生载流子的收集，从而提高光电二极管的检测性能。此外，由具有外延HBL的PSC制成的PIN光电二极管对40 keV、60 keV和80 keV X射线的灵敏度分别为7.08 mC Gy cm、4.04 mC Gy cm和2.38 mC Gy cm。
