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卤化物钙钛矿具有优异的电学和光学性能, 是光电子器件中理想的有源层候选材料, 特别是在高性能光探测方面显示出更具竞争力的发展前景, 其中全无机钙钛矿CsPbBr3因其良好的环境稳定性而被广泛关 注. 本文报道了一种具有快响应速度和低暗电流的垂直MSM型CsPbBr3薄膜光电探测器. 由于采用垂直 结构缩短了光生载流子的渡越距离, 器件具有超快的响应速度63 μs, 比传统平面MSM型光电探测器提高了两个数量级. 然后, 通过在p型CsPbBr3与Ag电极之间旋涂一层TiO2薄膜, 提升了界面光生载流子的分 离效率, 实现了钙钛矿薄膜与金属电极间的物理钝化, 从而大大降低了器件的暗电流, 在–1 V的偏压下暗电流只有–4.81×10–12 A. 此外, 该种垂直MSM型CsPbBr3薄膜光电探测器还具有线性动态范围大(122 dB)、探测率高(1.16×1012 Jones)和光稳定性好等诸多优点. 通过Sentaurus TCAD模拟发现, 电荷传输层可以选择性的阻挡载流子传输, 从而起到降低暗电流的作用, Sentaurus TCAD模拟结果与实验数据吻合, 揭示了电荷传输层降低器件暗电流的内在物理机制.Halide perovskites exhibit excellent electrical and optical properties and are ideal candidates for active layers in optoelectronic devices, especially in the field of high-performance photodetection, where they demonstrate a competitive advantage in terms of development prospects. Among them, the all-inorganic perovskite CsPbBr3 has received widespread attention due to its better environmental stability. It is demonstrated in this work that a vertical MSM-type CsPbBr3 thin-film photodetector has characteristics of fast response time and ultra-low dark current. The use of a vertical structure can reduce the transit distance of photo carriers, enabling the device to achieve a fast response time of 63 μs, which is two orders of magnitude higher than the traditional planar MSM-type photodetectors with a response time of 10 ms. Then, by spinning a charge transport layer between the p-type CsPbBr3 and Ag electrodes, effective separation of photocarriers at the interface is realized and physical passivation between the perovskite and metal electrodes is also achieved. Due to the superior surface quality of the spun TiO2 film compared with the NiOx film, and through Sentaurus TCAD simulations and bandgap analyses, with TiO2 serving as the electron transport layer, it effectively inhibits the transmission of excess holes in p-type CsPbBr3. Consequently, the electron transport layer TiO2 is more effective in reducing dark current than the hole transport layer NiOx, with a dark current magnitude of only –4.81×10–12 A at a –1 V bias. Furthermore, this vertical MSM-type CsPbBr3 thin-film photodetector also has a large linear dynamic range (122 dB), high detectivity (1.16×1012 Jones), and good photo-stability. Through Sentaurus TCAD simulation, it is found that the charge transport layer selectively blocks carrier transmission, thereby reducing dark current. The simulation results are in good agreement with experimental data, providing theoretical guidance for a more in-depth understanding of the intrinsic physical mechanisms.
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Keywords:
- CsPbBr3 /
- photodetector /
- vertical structure /
- low dark current /
- high response speed
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图 1 (a) 不同结构MSM型CsPbBr3薄膜光电探测器结构示意图; (b) 使用PLD制备的CsPbBr3薄膜的XRD扫描图; (c) CsPbBr3薄膜的紫外-可见吸收光谱图和荧光光谱图; (d) 平面MSM型CsPbBr3薄膜光电探测器响应速度图; (e) 垂直MSM型CsPbBr3薄膜光电探测器响应速度图; (f) 450 nm激光照射下, 垂直/平面MSM型CsPbBr3薄膜光电探测器的光暗电流图
Fig. 1. (a) Schematic diagram of MSM-type CsPbBr3 thin film photodetectors with different structures; (b) XRD patterns of CsPbBr3 thin films prepared using PLD; (c) UV-visible absorption spectrum and fluorescence spectrum of CsPbBr3 thin film; (d) response time graph of planar MSM-type CsPbBr3 thin film photodetector; (e) response time graph of vertical MSM-type CsPbBr3 thin film photodetector; (f) photo-dark current graph of vertical/planar MSM-type CsPbBr3 thin film photodetector under 450 nm laser illumination.
图 2 (a) CsPbBr3薄膜裸漏的表面扫描电子显微镜(SEM)图; (b)旋涂的NiOx薄膜表面SEM图; (c)旋涂的TiO2薄膜表面SEM图; (d)旋涂的TiO2薄膜断面SEM图; (e)如插图所示, –20 V偏压下, 与图(a), (b), 图(c)分别对应的器件电流-时间(I-T)曲线对比图
Fig. 2. (a) Scanning Electron Microscope (SEM) image of the exposed surface of CsPbBr3 thin film; (b) SEM image of the surface of spin-coated NiOx thin film; (c) SEM image of the surface of spin-coated TiO2 thin film; (d) cross-sectional SEM image of the spin-coated TiO2 thin film; (e) as illustrated, comparison of the device current-time (I-T) curves under a –20 V bias corresponding to panels (a), (b), (c).
图 3 (a) 不同界面缺陷态密度下垂直结构CsPbBr3薄膜光电探测器模拟暗电流曲线; (b) 加入一层NiOx薄膜后, CsPbBr3/NiOx薄膜器件总电流、电子电流和空穴电流的模拟I-V曲线图; (c) 加入一层TiO2薄膜后, CsPbBr3/TiO2薄膜器件总电流、电子电流和空穴电流的模拟I-V曲线图; (d)—(f) 与图(a), (b), (c)对应的光电探测器件内部电流分布图
Fig. 3. (a) Simulated dark current curves of vertical structure CsPbBr3 thin film photodetectors under different interface defect state densities; (b) after adding a layer of NiOx, simulated I-V curves showing total current, electron current, and hole current for CsPbBr3/NiOx thin film devices; (c) after adding a layer of TiO2, simulated I-V curves showing total current, electron current, and hole current for CsPbBr3/TiO2 thin film devices; (d)–(f) diagrams showing the distribution of internal current in photodetector devices corresponding to figures (a), (b), (c).
图 4 (a) CsPbBr3薄膜的紫外光电子能谱图; (b) CsPbBr3/NiOx薄膜光电探测器的能带图; (c) CsPbBr3/TiO2薄膜光电探测器的能带图; (d) 450 nm光照, 在黑暗和不同光照强度下垂直MSM型CsPbBr3薄膜光电探测器的I-V曲线图; (e) 450 nm光照, 在不同偏置电压下垂直MSM型CsPbBr3薄膜光电探测器的I-T曲线图; (f) 垂直MSM型CsPbBr3薄膜光电探测器的瞬态光响应曲线图
Fig. 4. (a) Ultraviolet photoelectron spectroscopy of CsPbBr3 thin films; (b) band diagram of CsPbBr3/NiOx thin film photodetectors; (c) band diagram of CsPbBr3/TiO2 thin film photodetectors; (d) I-V characteristics of vertical MSM-type CsPbBr3 thin film photodetectors under 450 nm illumination, in darkness and at various light intensities; (e) I-T curves of vertical MSM-type CsPbBr3 thin film photodetectors under 450 nm illumination at different bias voltages; (f) transient photocurrent response curves of vertical MSM-type CsPbBr3 thin film photodetectors.
图 5 (a) 450 nm光照和–20 V偏置, 不同光照强度下垂直MSM型CsPbBr3薄膜光电探测器的光电流的绝对值大小; (b) 不同光照强度下的开关比; (c) 不同光照强度下的响应度; (d) 不同光照强度下的探测率
Fig. 5. (a) The absolute magnitude of the photocurrent in vertical MSM-type CsPbBr3 thin film photodetectors under 450 nm illumination and a -20 V bias at different light intensities; (b) on/off ratio at different light intensities; (c) responsivity at different light intensities; (d) detectivity at different light intensities.
表 1 CsPbBr3基薄膜光电探测器的性能对比
Table 1. Performance comparison of CsPbBr3-based thin film photodetectors.
Detector Structure Dark current/(10–10 A) D*/(109 Jones) τrise/τfall/(ms/ms) Ref. CsPbBr3 NPLs/Ag Planar –0.37(–3 V) 9300 75/72 [35] n-Si/CsPbBr3/Au Planar 0.003(0 V) 105 190/291 [36] 1D-TiO2/0D-CsPbBr3/Au Planar 4(1 V) 1800 9348/5951 [37] CsPbBr3/ZnO Vertical –5(–5 V) 7 0.061/1.4 [38] SnO2/CsPbBr3/Carbon Vertical 330(0 V) 370 0.11/0.23 [39] CsPbBr3/TiO2/Ag Vertical –0.0481(–1 V) 1160 0.063/0.162 This work -
[1] Xu J, Li J, Wang H S, He C Y, Li J L, Bao Y N, Tang H Y, Luo H D, Liu X C, Yang Y M 2021 Adv. Mater. Interfaces 9 2101487Google Scholar
[2] Zhang Y, Wu C Y, Zhou X Y, Li J C, Tao X Y, Liu B Y, Chen J W, Chang Y J, Tong G Q, Jiang Y 2023 Mater. Today Phys. 36 101179Google Scholar
[3] Liu X Y, Liu Z Y, Li J J, Tan X H, Sun B, Fang H, Xi S, Shi T L, Tang Z R, Liao G L 2020 J. Mater. Chem. C 8 3337Google Scholar
[4] Perumalveeramalai C, Zheng J, Wang Y, Guo H L, Pammi S. V. N., Mudike R, Li C B 2024 Chem. Eng. J. 492 152213Google Scholar
[5] Wang Y Z, Kublitski J, Xing S, Dollinger F, Spoltore D, Benduhn J, Leo K 2022 Mater. Horiz. 9 220Google Scholar
[6] Zheng J B, Yang D Z, Guo D C, Yang L Q, Li Ji, Ma D G 2023 ACS Photonics 10 1382Google Scholar
[7] Wang H D, Huang H X, Zha J J, et al. 2023 Adv. Opt. Mater. 11 2301508Google Scholar
[8] Gong W Q, Tian Y Z, Yan J, Gao F, Li L 2022 J. Mater. Chem. C 10 7460Google Scholar
[9] Qiao S, Liu J H, Wang R N, Guo L J, Wang S F, Pan A L, Pan C F 2023 Adv. Opt. Mater. 11 2300751Google Scholar
[10] Li X, Xiang Y, Wan J X, Xiao Z X, Yuan H, Sun J, Liu Y F, Dai G Z, Yang J L 2022 Org. Electron. 101 106409Google Scholar
[11] Zhu L P, Cheng X M, Wang A W, Shan Y S, Cao X L, Cao B Q 2023 Appl. Phys. Lett. 123 212105Google Scholar
[12] Hu T G, Zhao L X, Wang Y J, Lin H L, Xie S H, Hu Y, Liu C, Zhu W K, Wei Z M, Liu J, Wang K Y 2023 ACS Nano 17 8411Google Scholar
[13] Zhao Z E, Tang W B, Zhang S H, Ding Y C, Zhao X F, Yuan G L 2023 J. Phys. Chem. C 127 4846Google Scholar
[14] 王爱伟, 祝鲁平, 单衍苏, 刘鹏, 曹学蕾, 曹丙强 2024 物理学报 73 058503Google Scholar
Wang A W, Zhu L P, Shan Y S, Liu P, Cao X L, Cao B Q 2024 Acta Phys. Sin. 73 058503Google Scholar
[15] Yan T T, Liu X Y, Zhang X Y, Hong E L, Wu L M, Fang X S 2023 Adv. Funct. Mater. 34 2311042Google Scholar
[16] Saleem M I, Sulaman M, Batool A, Bukhtiar A, Khalid S 2023 Energy Technol. 11 2300013Google Scholar
[17] Yuan B L, Wei H M, Li J W, Zhou Y, Xu F, Li J K, Cao B Q 2021 ACS Appl. Electron. Mater. 3 5592Google Scholar
[18] Ahirwar P, Kumar R 2023 Chem. Phys. Lett. 810 140180Google Scholar
[19] Bai T X Y, Wang S W., Bai L Y, Zhang K X., Chu C Y., Yi L X. 2022 Nanoscale Res. Lett. 17 69Google Scholar
[20] Yun K R, Lee T J, Kim S K, Kim J H, Seong T Y 2022 Adv. Opt. Mater. 11 2201974Google Scholar
[21] Mukhokosi E P, Maaza M 2022 J. Mater. Sci. 57 1555Google Scholar
[22] Sathyanarayana S, Krishnan K N, Das B C. 2024 Phys. Rev. Appl. 21 044015Google Scholar
[23] Cai J, Zhao T, Chen M M, Su J Y, Shen X M, Liu Y, Cao D W 2022 J. Phys. Chem. C 126 10007Google Scholar
[24] Zhou H P, Chen M W, Liu C G, Zhang R, Li J, Liao S A, Lu H F, Yang Y P 2023 Discover Nano 18 11Google Scholar
[25] Bhardwaj B, Bothra U, Singh S, Mills S, Ronningen T. J., Krishna S, Kabra D 2023 Appl. Phys. Rev. 10 021419Google Scholar
[26] Liu T, Li C, Yuan B L, Chen Y, Wei H M, Cao B Q 2022 Appl. Phys. Lett. 121 012102Google Scholar
[27] Alnuaimi A, Almansouri I, Nayfeh A 2016 J. Comput. Electron. 15 1110Google Scholar
[28] Wang T, Xiao J G, Sun R, Luo L B, Yi M X 2022 Chin. Phys. B 31 018801Google Scholar
[29] Luo X L, Hu Y, Lin Z H, Guo X, Zhang S Y, Shou C H, Hu Z S, Zhao X, Hao Y, Chang J J 2023 Solar RRL 7 2300081Google Scholar
[30] Liu X Y, Li S Y, Li Z Q, Cao F, Su L, Shtansky D V, Fang X S 2022 ACS Appl. Mater. Interfaces 14 48936Google Scholar
[31] 胡紫婷, 舒鑫, 王香, 李跃, 徐闰, 洪峰, 马忠权, 蒋最敏, 徐飞 2022 物理学报 71 116801Google Scholar
Hu Z T, Shu X, Wang X, Li Y, Xu R, Hong F, Ma Z Q, Jiang Z M, Xu F 2022 Acta Phys. Sin. 71 116801Google Scholar
[32] Li G X, Wang Y K, Huang L X, Sun W H 2022 J. Alloys Compd. 907 164432Google Scholar
[33] Wang S L, Li M Y, Song C Y, Zheng C L, Li J T, Li Z Y, Zhang Y T, Yao J Q 2023 Appl. Surf. Sci. 623 156983Google Scholar
[34] Yuan Y, Ji Z, Yan G H, Li Z W, Li J L, Kuang M, Jiang B Q, Zeng L L, Pan L K, Mai W J 2021 J. Mater. Sci. Technol. 75 39Google Scholar
[35] Wang H, Du Z T, Jiang X, Cao S, Zou B S, Zheng J J, Zhao J L 2024 ACS Appl. Mater. Interfaces 16 11694Google Scholar
[36] Hua F, Du X, Huang Z Y, Gu Y T, Wen J F, Liu F C, Chen J X, Tang T 2023 J. Opt. Soc. Am. B: Opt. Phys. 41 55Google Scholar
[37] Zhang T, Cai S Y, Liang N N, Gao Y L, Li Y P, Liu F C, Long L Z, Liu J 2023 Phys. Scr. 99 015526Google Scholar
[38] Su L X, Li T F, Zhu Y 2022 Opt. Express 30 23330Google Scholar
[39] Zhou H, Wang R, Zhang X H, Xiao B A, Shuang Z H, Wu D J, Qin P L 2023 IEEE Trans. Electron Devices 70 6435Google Scholar
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