Research On The Performance Of Photovoltaic Photodetectors Based On Two-dimensional Perovskites

Photodetectors have a wide range of needs in medicine,display imaging,military,optical communication,infrared measurement and other fields.At present,most of the photodetectors used in the market are based on traditional inorganic semiconductor materials such as silicon and gallium arsenide,but their fabrication process is complicated,the cost is high,and the mechanical flexibility is poor.The organic-inorganic hybrid perovskite material has good optical,electrical and mechanical properties,and low preparation cost,therefore,is an ideal material for the preparation of photodetectors.Especially,two-dimensional perovskite materials have better stability than three-dimensional perovskite materials owing to the hydrophobic organic functional groups in their structure.In recent years,a series of photodetectors based on2D perovskite have been reported.Most of the reported two-dimensional perovskite photodetectors are based on planar structures,and there are few reports on vertical photovoltaic two-dimensional perovskite photodetectors.Photovoltaic photodetectors typically have faster response times than planar photoconductive photodetectors,while having lower dark current and greater linear dynamic range.In this thesis,a photovoltaic photodetector based on two-dimensional perovskite is studied,focusing on the factors affecting its response time and extending its response band to the near-infrared（NIR）region.In order to explore the reasons that affect the response time of the device,we prepared photodetectors with different thicknesses of active layers and characterized their performance by adjusting the concentration of the active layer precursor solution.Next,we introduced Y6material and successfully broadened the response band of the device to the NIR region.The specific research content is divided into two parts:（1）Improve device response time.In this paper,the response speed of the device is improved by reducing the thickness of the active layer and reducing the effective area of the device.By changing the thickness of the active layer,the purpose of reducing the carrier transit distance in the device is achieved,and the response time of the device is reduced.However,as the thickness of the active layer decreases,the quality of the active layer film decreases,which together with the carrier transport distance restricts the response time of the device.Finally,the device with an active layer thickness of 80 nm is the optimal device,with a rise time of 21 ns and a fall time of 422 ns.Next,we continuously reduce the effective area of the device by changing the electrode area on the top.With the continuous reduction of the effective area of the device,the capacitance C of the device decreases,and the response time of the device also decreases.The optimal device has a rise time of 17 ns and a fall time of 116 ns.（2）Broaden the response band.In this paper,the response band of the device is broadened to the NIR region by the non-fullerene functional layer.We fabricated photodetectors with the structure ITO/PTAA/Al₂O₃/Perovskite/Y6/BCP/Ag.By introducing Y6,a non-fullerene material that absorbs at NIR,the EQE,R,and D^*of the device all show strong peaks at 850nm.The device has a continuous response under 850 nm LED laser irradiation,indicating that the device can work continuously and stably in the NIR region.The device still has a fast response time under the femtosecond laser,with a rise time of 46 ns and a fall time of 489 ns.