【作者】 丁洁；

【导师】 严清峰；

【作者基本信息】 清华大学 ， 化学， 2019， 博士

【摘要】 作为新一代的半导体光电材料,有机-无机杂化钙钛矿以其高载流子迁移率、长的载流子扩散长度和大的光吸收系数等优异特性引起了研究者们极大的兴趣。将新型半导体材料应用在光电探测器以提升器件性能一直是研究的热点。下一代光电探测器正朝着自驱动、高响应度、快响应速度、低噪声、宽响应波段及柔性等方向发展。与多晶薄膜相比,钙钛矿单晶具有更低的缺陷态密度并且没有晶界,有望进一步提升钙钛矿光电探测器的性能。本文以有机-无机杂化卤化物钙钛矿单晶为基础制备了一系列光电探测器,并对其驱动方式、响应时间、功能性、噪声特性、柔性展开研究,主要研究内容如下:通过在溶液法生长的CH₃NH₃PbI₃单晶表面构筑不对称电极Au和Al,首次实现了自驱动的CH₃NH₃PbI₃单晶光电探测器。利用金属/钙钛矿之间的肖特基接触,有效地建立起内建电场。不加偏压的情况下,探测器的响应度达到0.24 A/W,并实现了全可见光谱（375 nm～808 nm）范围响应。基于氯离子辅助溶液法生长的高品质CH₃NH₃PbI₃单晶,制备了平面型光电导光电探测器。通过改进传统的光电测量平台,用脉冲激光代替原有的连续激光光源,用采样频率更高的示波器作为测量仪器,大幅提高了光电平台的测量响应极限,从而确认了CH₃NH₃PbI₃单晶光电探测器的响应时间真实值应低于12.5 ns。在大尺寸CH₃NH₃PbI₃单晶的表面上制备了2*2光电探测器阵列。利用相邻两个光电探测器对运动物体的响应时间差,实现了速度传感的功能。对一个运动速度41.67 m/s的物体,测量的相对误差仅为0.3%。五个月后,性能保持稳定。制备了一系列平面结构的混卤CH₃NH₃Pb(Br_1-xCl_x)₃,CH₃NH₃Pb(I_1-xBr_x)₃单晶光电探测器,通过快速傅立叶变换计算器件的噪声。分析噪声频谱探讨了卤素掺杂对噪声的影响,发现氯掺杂最多的单晶具有最大的噪声和最低的探测灵敏度。利用CH₃NH₃PbI₃单晶在生长母液中室温下不稳定的特点,将其水解产物脱水得到CH₃NH₃PbI₃微米线。将CH₃NH₃PbI₃微米线与石墨烯结合,成功制备首个可拉伸的杂化钙钛矿光电探测器。该光电探测器在拉伸度0%到100%下能够正常工作。拉伸度50%的情况下,经过100个循环,器件仍能正常工作。更多还原

【Abstract】 As a new generation of semiconductor optoelectronic materials,organic-inorganic hybrid halide perovskites have attracted amounts of interest due to their high carrier mobility,long carrier diffusion length and larg e optical absorption coefficient.The application of new semiconductor materials in photodetectors to improve their performance has been a hot topic.Next-generation photodetectors are moving toward self-driving,high responsivity,fast response speed,low noise,broad spectral response and flexibility.Compared to polycrystalline thin films,perovskite single crystals have a lower density of trap states and no grain boundaries.They are thus expected to be able to further enhance the performance of perovsk ite photodetectors.In this thesis,organic-inorganic halide perovskite single crystals were grown and photodetectors based on these single crystals were explored.The main research contents are as follows:For the first time,a self-driven photodetector was realized by fabrication an asymmetric electrode Au-Al on the surface of the CH₃NH₃PbI₃ single crystal.The built-in electric field was effectively established by the Schottky contact between the metal and perovskite.Without bias,the response speed of the detector was 0.24 A/W.Also,it showed response within full visible spectral（375 nm～808 nm）.A planar photoconductive photodetector is prepared based on the high-quality CH₃NH₃PbI₃ single crystal grown by solution growth method assisted by chloride ion.A modified optoelectronic measurement platform was set up,in which a pulsed laser was used to replace the conventional continuous laser source,and the oscilloscope with higher sampling frequency was used as the measuring instrument.In this way,the measurement response limit of the optoelectronic platform has been greatly improved,Benif ited from the combination of the high-quality CH₃NH₃PbI₃single crystal and the greatly improved response limit of the ptoelectronic measurement platform,the real response speed of the CH₃NH₃PbI₃single crystal photodetector was measured to be less than 12.5 ns.A 2*2 photodetector array was prepared thanks to the large size and uniformity of the as-grown CH₃NH₃PbI₃ single crystal.For the first time,a speed sensor was demonstrated based on such a photodetector array.The velocity of a moving object could be calculated by the response delay between two adjacent photodetectors.In addition,capturing the trajectory of a moving object was also demonstrated.Detector noise is the key for detector sensitivity.The dark current of a photodetector determines its noise.We used methyl mixed halide perovskite CH₃NH₃Pb(Br_1-xCl_x)₃,CH₃NH₃Pb(I_1-xBr_x)₃ single crystal as the research object.The noise of a series of photodetectors based on methyl mixed halide perovskite single crystals was studied by Fast Fourier Transform.The influence of halogen doping on device noise was discussed by analyzing the noise situation.The photodector based on CH₃NH₃PbI_3-xCl_xsingle crystal with the most chlorine doping was found to have the highest noise and the lowest detection se nsitivity.The solution-grown CH₃NH₃PbI₃ single crystal was found not stable when it was stored at mother liquor at room temperature.The bulk CH ₃NH₃PbI₃single crystal tended to form hydrolyzed product which changed to CH ₃NH₃PbI₃microwires after dehydration.The CH₃NH₃PbI₃ microwires were combined with graphene and transferred to a stretchable substrate.A stretchable perovskite photodetector was successfully prepared for the first time.At 100%strain,the device still worked.With a 50%stretch,the de vice still could operate normally after 100 cycles.更多还原