Preparation And Properties Study Of The Photodetector Based On Hybrid Perovskite CH₃NH₃PbI₃ And Organic Polymer

Hybrid perovskite photodetectors and organic polymer photodetectors?OPDs?take the advantages of low cost,light weight,wider material selectivity,and good flexibility,which is paid more attention by people.After people's unremitting efforts,the performance of the two types of photodetectors gradually was improved.However,for hybrid perovskite photoelectric detector,its material calcium most concentrated in polycrystalline perovskites,because of their multi-grain boundary and defect density leading to device instability.Therefore,in order to solve this problem,this paper was prepared based on MAPbI₃ perovskite crystal photodetector,its performance compared with the traditional polycrystalline perovskite devices have improved significantly,and systematically studied the influence factors of the single crystal growth;For organic polymer photodetectors with low photoresponse,an organic photosensitive phototransistor with high mobility and photoresponsivity was prepared by using surface plasmon resonance effect.The effects of gold nanoparticles and polymer interface on the photoelectric properties of the device was studied.The creative research work is summarized as follows:?1?To solve the problem of limiting the applications of the photovoltaic device due to the growth of the single crystal with the small size by the CVD method,large-size high-quality MAPbI₃ single crystals have been grown by modifying the surface of the substrate to control the nucleation position.Preparation of PbI₂ single crystal.The influencing factors of single crystal growth were studied by physical vapor deposition?PVD?system,including temperature,pressure,flow rate of carrier gas and temperature gradient.The substrate temperature and pressure on the crystal growth is a key factor.The best substrate temperature for crystal growth is 350?and the pressure is 250 Pa.However,the crystal grows along the edge of the substrate.For the convenience of testing,OTS modification is performed on the surface of the substrate by using the lowest surface energy principle of crystal nucleation to realize the controllability of the crystal nucleation position and thickness.The thickness is controlled at 35-700 nm and the optimum growth time required for device preparation is 20 min with an optimum flow rate of 20 sccm.Preparation and characterization of MAPbI₃ single crystal.Compared with the reported perovskite single crystal size,the best growth conditions of MAPbI₃perovskite single crystals transformed by solid-gas interface reaction was 140 min,and MAPbI₃ single crystal with the large-area of up to12000?m² was grown.Then MAPbI₃ monocrystalline characterization showed that the surface of the crystal was smooth,with less defect density and longer exciton diffusion?4.65 ns?.In addition,the perovskite single crystalline was measured by XRD when exposed to air for 80 days or more.Although the characteristic peaks were different in size,the crystal did not make changes as a whole,showing the characteristic peak of the MAPbI₃ single crystal,which confirmed the high quality and large size of MAPbI₃ single crystal.?2?Through the investigations into the photoelectric properties of MAPbI₃single crystals by three kinds of metal electrodes?Au,Ag,Cu?,it is concluded that the stability of the photodetector device is achieved by the Au electrode,and the photocurrent can be rapidly increased by the Ag electrode,resulting in the improvement of the responsivity.Effect of Au electrode on the photodetector properties of the of MAPbI₃single crystal.It is found that the photoelectric characteristic of the device has certain selectivity to visible light in different wavelength ranges.It displayed a high sensitivity to 500 nm with an external quantum efficiency of 9034%,a responsivity of 36.5 A/W,a detection rate of 1.1×10¹44 J,a switching ratio of more than 10⁴,and a very low dark current for 10^-1414 A,which make the device a higher external quantum efficiency per unit time compared with currently reported higher values.The interface between Au electrode and perovskite single crystal not only achieved ohmic contact but also exhibited good protective effect.The photoelectric performance of the device was studied,and it was concluded that after 30 days,the photocurrent of the device still tended to be stable without any decay.Effect of Ag electrode on the photodetector properties of the of MAPb I₃single crystal.The high quality single crystal displayed the rapid increase of photocurrent under illumination in the Ag electrode,which is 3-4 orders higher than that of the Au electrode,which may be attributed to the relatively low work function and the lower energy required for electron excitation,gathering more charge close to the electrodes in the narrower area.The responsivity increased from 3.8×10⁴ A/W to up to 2.7×10⁵ A/W with the increase of light intensity and showed a faster response time?0.03 s rise time and 0.15 s fall time?.However,the electrode is not stable under illumination and the MAPbI₃ single crystal becomes black over a period of time.More serious is the Cu electrode in the light and heat irradiation,the single crystal is black in a short period of time,and in the radiation is high,the crystal will turn completely black,thus losing any photoelectric properties.?3?Based on the surface plasmon resonance effect,a method for obtaining high performance phototransistor based on organic semiconductor with no visible light response?or weak visible light response?was established.Au NPs were prepared in situ on the substrates and used to fabricate Phot-OFET directly.By utilizing the surface plasmon resonance effect of the Au NPs,high performance Phot-OFET with a mobility of 0.12 cm²/V·s and a responsivity of 11.6 A/W was obtained successfully based on organic semiconductor materials without photo-response in the visible spectrum.The surface chemical modification of gold nanoparticles with alkane thiol played a key role in improving the device performance.