Preparation And Photoelectric Properties Of High Performance Perovskite Solar Cells In Air Environment

Rapid improvement in photoconversion effciency（PCE）of solution processable organometallic hybrid halide based perovskite solar cells（PSCs）have taken the photovoltaic（PV）community with a surprise.This class of materials,possess several unique features for photovoltaic applications,such as electron-hole ambipolar diffusion,long carrier lifetime,tunable bandgap and excellent tolerability of defect.The conversion efficiency of perovskite solar cells can be comparable with silicon solar cell.However,perovskite materials are sensitive to moisture and oxygen,leading to the fabrication of parovskite solar cells usually carried out under high vacuum conditions.It will raise the cost and hinder the the commercialization of perovkite solar cells.In this paper,two different methods,which are the application of anti-solvent in one-step solution process and doping of non-metallic cation into perovskite material,were employed to prepare perovskite solar cells with high-efficiency under fully air environment.The influence of different anti-solvent and different concentration of Si⁴⁺on the micro morphology of perovskite layer,crystallinity,optical properties and the photovoltaic performance of the device is discussed in detail.The main findings are as follows:1、The influence of four different anti solvents on photoelectric properties of CH₃NH₃PbI₃ perovskite solar cells prepared under high relative humidity:In this paper,four different anti-solvents,chlorobenzene,toluene,ether and ethyl acetate were applied under the relative humidity higher（RH）than 50%and the influence on the micro morphology of perovskite layer,crystallinity,optical properties and the photovoltaic performance of the device is discussed in detail.We compared the perovskite solar cells fabricated via the four anti-solvents mentioned above.It is found that,under high humidity,the devices prepared via chlorobenzene,toluene and ether display the conversion efficiency of 2.87%,0.2%and 13.78%,respectively.In contrast,the controlled sample fabricated via ethyl acetate displays a conversion efficiency as high as17.83%.The discrepancy in performance can be ascribed to the moisture tolerance of ethyl acetate,which can quickly remove the PbI₂-MAI-DMSO intermediate phase produced in the process of perovskite nucleation.Therefore,the enlarged grain size and decrease of grain boundary in perovskite interface can be beneficial to carrier transport and suppressing electron recombination,which leads to the improvement in photovoltaic properties of the devices.2、The influence of doping concentration of Si⁴⁺on the photoelectric properties of perovskite solar cells:In this study,we prepared the perovskite film layer doped with different concentration,0.1mol%、0.15mol%、0.3mol%、0.6mol%、1.2mol%of Si⁴⁺and the controlled and uncontrolled samples were characterized by XRD、SEM、EDS、UV-vi and IPCE.The results display that the micro morphology,crystallinity and optical absorption of perovskite sample are improved as the ratio of Si⁴⁺doping increasing from 0%to 0.3%.By contrast,crystallinity and optical absorption of perovskite sample decrease as the ratio of Si⁴⁺doping still increases from 0.3%to 1.2%.Based on the doping films,planar perovskite solar cells were fabricated under high relative humidity.The results indicate that the conversion efficiency of device doped with 0.3%Si⁴⁺is18.37%,15%higher than that of the undoped device.As the doping ratio of Si⁴⁺increases from 0.3%to 1.2%,the performance of the solar cells deteriorates,which is consistent with the results obtained before.The deviation in the device performance can be ascribed to the formation of SiO₂ located in the interface of perovskite layer can passivate grain boundary and densify the perovskite layer,resulting from the optimized Si⁴⁺dopant in perovskite film.The improvement of the efficiency of the controlled（doped）samples is originated from the decrease of defect traps,leading to suppressing of carrier recombination in favour of electron transport process.