Research On Interface Control Of Halide Perovskite-based Photovoltaic Devices

Photodetectors as the important device of photoelectric converter play an essential role in the fields of modern industry and science research.The parameters such as detectivity,on/off ratio,response time,and stability have a high requirement in the practical application of photodetector.Perovskite is a new photoelectric material,it has a lot of better optoelectronics performances,for example,good external quantum efficiency（EQE）,high light absorption spectrum,excellent light absorbance,adjustable light bandgap.The preparation process of perovskite devices is simple and low-cost,which is very suitable for the preparation of photoelectric devices.Many researchers have applied it to solar cells（PSCs）,photodetectors,lasers,light-emitting diodes,and it proved wide business prospects.Compared with traditional detectors,perovskite photodetectors have a simpler and lower-cost process.In the past few years,perovskite devices got many breakthroughs in photovoltaic especially vertical structure perovskite devices have attracted much attention due to their self-powered properties,which provide a new technical path and application mode for many fields such as photoelectric photodetectors.Many reports prove that organic-inorganic hybrid halide PSCs have not high stability against heat and humidity.In order to ensure the stability of the device,in this paper,by the methods for modifying and doped the perovskite layer,we used the all-inorganic perovskite materials CsPbIBr₂ to make the devices and research the development of optoelectronic performance.The main work of this paper is as follows:1.The device’s substrate was modified by polyethyleneimine（PEI）.In this paper,used PEI to modify the fluorine-doped tin oxide（FTO）,which uses the dipole moment to adjust the work function of the layer.The work function of FTO decreased from 4.52 eV to 4.25eV,so the energy levels between the layer of the interface and perovskite match better.Photogenerated carriers can be more easily transferred to the electrodes of the device.The dark current of the devices has obviously reduced.The structure of the device is simplified as FTO/CsPbIBr₂/Carbon,which abandoned the transport layers.The structure of the device is simplified as FTO/CsPbIBr₂/Carbon,and the detectivity can still reach 3.74×10¹² Jones.2.The PEI was incorporated into the perovskite precursor.After a small amount of PEI aqueous solution with a high concentration is doped into the perovskite precursor solution,the bottom conduction band energy level of the CsPbIBr₂ film is reduced by 0.1eV,the energy level is better matched the energy levels between the perovskite and other layers changed more closely.The film grains are changed more uniform,the dark current of the device is reduced to 3.12×10^-10 A,and the maximum detectivity is 6.01×10¹² Jones.3.A new layer was introduced in the device.In this paper,as the ultra-wide gap band semiconductor,Ga₂O₃ was introduced as the interface layer between the electron transport layer and the perovskite.The gap width of Ga₂O₃ is large,but the conduction band bottom energy level is similar to perovskite so that the photo-generated electrons are easy to pass through the Ga₂O₃ layer and finally enter the negative pole,while the holes are blocked by the gallium oxide layer,which greatly reduces the recombination of the electron holes at the interface.The dark current of the photodetector is greatly suppressed.The photodetector has a low dark current of 4.15×10^-9 A and the peak detectivity is 1.83×10¹² Jones.This experiment also provides a new idea for the combination of ultra-wideband gap semiconductor materials with perovskite.