| Photodetector is a kind of photoelectric device that converts optical signals into electrical signals,which can identify light under specific light intensity and wavelength.It is widely used in environmental detection,image sensing,optical communication and other fields.Perovskite materials have high light absorption coefficient,considerable carrier diffusion length,adjustable optical band gap,simple preparation method and many other advantages,which make it one of the alternatives to traditional semiconductor materials.Although organic-inorganic hybrid perovskite materials have numerous attractive advantages,there are still some urgent problems to be solved,such as a large number of defects in the bulk phase and interface,poor film stability and insufficient light absorption range of perovskite films prepared by solution method.In order to promote the commercialization of perovskite optoelectronic devices,it is necessary to improve the performance and stability of the device and broaden the response spectral range.The perovskite layer acts as the light-absorbing layer of the photodetector,and its film quality,light-absorbing range,and energy level matching with other layers ultimately determine the optoelectronic properties of the device.Therefore,it is important approaches for highperformance broadband photodetectors by improving the quality of perovskite films,promoting the extraction and transport of carriers,and broadening the absorption spectrum of perovskite.To address the above problems,this dissertation mainly carries out the following works:1.High quality films based on P3HT/perovskite heterojunction were prepared by antisolvent method.On this basis,optoelectronic devices with ITO/SnO2/perovskite/P3HT/Spiro-OMeTAD/Ag structure were prepared.Through compared with perovskite without P3HT,it was found that,firstly,P3HT infiltration at the grain boundary can effectively passivate the perovskite film,reduce the defect density,and improve the film quality and light absorption ability;Secondly,by measuring and calculating the energy level of the perovskite film,it is found that P3HT can regulate the energy level on the perovskite surface to make it better match with the hole transport layer Spiro-OMeTAD,which is conducive to the extraction and transmission of carriers and reduce recombination.The maximum responsivity and detectivity of the optimized device are 0.41 A/W and 0.61 A/W×1012 Jones(700 nm)respectively,which is 2 and 6 times respectively that of not optimized devices;In addition,P3HT is a hydrophobic material.P3HT partially staying on the perovskite surface can effectively improve the stability of films and devices.After being placed in the air environment(10-20%humidity,room temperature environment)for 720h,the optimized device still retains about 78%of the initial photocurrent,which is much better than the not optimized device.2.In order to broaden the response spectrum range of Pb-based perovskite,Sn is doped into perovskite in this paper.However,SnI2 is easier to react with MAI,resulting in too fast nucleation crystallization rate and poor film quality.Secondly,Sn2+is easy to be oxidized to Sn4+,which would bring more defects and increase the band gap of the film.In order to solve these problems,MACl is added to the Pb-Sn mixed perovskite precursor solution.MACl not only makes the precursor solution more stable and inhibits the oxidation of Sn2+in the solution.but also greatly delay the nucleation crystallization rate of Pb-Sn perovskite,which is helpful to obtain high-quality perovskite films without holes.Even if the doped Sn content increases,compared with the devices without MACl,the photocurrent increases and the dark current decreases of the devices with MACl.In addition,the stability of devices based on MAPbo.9Sn0.1I3 was tested.The test results show that the photocurrent value of devices with MACl is still 75%of the initial value after being placed in air environment for 408 h,which is much higher than that of devices without MACl. |
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