基于CuSCN/Cs_(3)Bi_(2)I_(6)Br_(3)纳米薄膜的p-i-n型光电探测器

All-inorganic p-i-n Photodetector Based on Lead-free CuSCN/Cs_(3)Bi_(2)I_(6)Br_(3)Nanofilm

卤化铅钙钛矿具有高光吸收系数、长载流子扩散长度和高荧光量子效率等优异光电特性,成为当下光电探测器(PDs)研究领域的热点。但卤化铅钙钛矿的高生物毒性和低环境稳定性制约了该类器件的发展和应用,因此寻找低毒稳定的材料尤为重要。到目前为止,Sn、Ge、Sb、Bi等材料都已得到研究,其中铋基钙钛矿因其稳定、无毒和宽带隙等特性成为候选材料之一。影响PDs性能的因素很多,其中抑制暗电流是提升器件性能的重要手段之一。本文通过溶液旋涂无机化合物CuSCN取代传统PEDOT∶PSS作为空穴传输层(HTL),制备了结构为ITO/CuSCN/Cs_(3)Bi_(2)I_(6)Br_(3)/Zn O/Ag的p-i-n型光电探测器。CuSCN最低未占分子轨道(LUMO)能级为-1.5 e V,与ITO电子注入势垒高达3.3 e V,远高于PEDOT∶PSS与ITO的电子注入势垒(1.8 e V),反向偏压下工作更能有效阻挡电子从ITO电极的注入,因此降低了探测器的暗电流。器件在自供电条件425 nm单色光照射下光电流达6.87×10^(-6)A,暗电流低至3.52×10^(-11)A,开关比超过10~5,相比于基于PEDOT∶PSS空穴传输层的探测器提升了2个数量级。此外,该探测器的上升和下降时间都小于0.12 s,均优于基于PEDOT∶PSS空穴传输层的探测器,这可归因于CuSCN比PEDOT∶PSS具有更高的载流子传输迁移率。结果表明,ITO/CuSCN/Cs_(3)Bi_(2)I_(6)Br_(3)/Zn O/Ag结构的光电探测器具有自供电、高开关比、稳定、无毒等优点,为实现商业化提供了一种可行策略。

Lead halide perovskite is a popular research field in photodetectors(PDs)due to its excel⁃lent photoelectric characteristics such as high light absorption coefficient,long carrier diffusion length and high fluorescence quantum efficiency.However,heavy biological toxicity and low envi⁃ronmental stability restrict the development and application of this kind of devices.So far,Sn,Ge,Sb,Bi and other materials have been studied,in which bismuth-based perovskites have become one of the candidate materials due to stability,non-toxicity and wide band gap.The performance of PDs is limited by many factors,and dark current suppression is one of the important means to improve device performance.Based on the traditional hole transport layer(HTL)of PEDOT∶PSS replaced by the inorganic compound CuSCN through spin-coating,the p-i-n type photodetectors with an architec⁃ture of ITO/CuSCN/Cs_(3)Bi_(2)I_(6)Br_(3)/ZnO/Ag were fabricated.CuSCN can effectively block electron inject⁃ing through the interface between the hole transport layer and the perovskite absorption layer,be⁃cause the lowest unoccupied molecular orbital(LUMO)energy level of CuSCN is-1.5 eV,the elec⁃tron injection barrier with ITO is as high as 3.3 eV,which is much higher than that of PEDOT∶PSS and ITO(1.8 eV).Under self-powered condition,the dark current of the device was as low as 3.52×10^(-11)A.Its on/off ratio reaches 105,which is two orders of magnitude higher than the detector of PEDOT∶PSS.In addition,the rise and fall time of the detector are less than 0.1 s and 0.12 s,which are better than the detector of PEDOT∶PSS.This result can be attributed to the higher carrier transport mobility of CuSCN higher than PEDOT∶PSS.The results show that the structure of ITO/CuSCN/Cs_(3)Bi_(2)I_(6)Br_(3)/ZnO/Ag photodetector posseses many characteristics,such as self-driven,high on/off ratio,non-toxic and stable.It provides a feasible strategy for realizing commercialization.