Modification Of CH₃NH₃PbI₃ Perovskite Materials And Preparation Of Solar Cells And Study On Photovoltaic Performance

The organic-inorganic hybrid perovskite material ABX₃（A=CH₃NH₃（MA）,B=Pb,Sn,X=I）was attracted extensive attention in academia and industry due to its advantages of high photoelectric conversion efficiency,low cost,simple and diversified solution preparation.The improvement of perovskite crystal film quality is the key point to improve the performance of perovskite solar cells（PSCs）.Therefore,this paper mainly focuses on the crystal quality optimization of perovskite film.Based on this,we mainly sensitize the perovskite active layer by adding a sensitizer and uses dopants to improve the crystallinity and decrease the pinhole of the perovskite active layer in this paper.The effect of crystal morphology and optical property on cells performance were investigated by the corresponding characterization,such as XRD patterns,SEM images,UV-vis absorptionspectra,PL spectra and J-V characteristics.The following research works were carried out to improve the efficiency.（1）The studies on SnS quantum dots（QDs）sensitized CH₃NH₃PbI₃（MAPI）solar cells.The SnS QDs were synthesized by a using reflux method.The obtained SnS QDs were added into MAPI precursor solution,and the perovskite layer was prepared by one-step spin-coating method for optimization,the obtained high-quality active layer was used to prepare the perovskite solar cells with the structure of FTO/Ti O₂/SnS QDs-MAPI/Carbon.Finally,the effect of perovskite layer on cells performance was study.The SEM images showd that,the perovskite film presented denser surface,reduced grain boundaries and without obvious holes after adding SnS QDs.With the crystal size of about 1.5μm,the perovskite film presented better crystallinity and light absorption properties.Compared with the pristine device and improve the device efficiency（S₅）with about 59%,which was attributed to the addition of SnS QDs into the perovskite can reduce the charge recombination rate of the perovskite,realize more effective charge extraction.（2）The studies on Cd_xSn_（1-x）S quantum dots（QDs）sensitized MAPI solar cells.Cd_xSn_（1-x）S alloy QDs were prepared by a reflux method.The obtained QDs were added into the perovskite precursor solution（MAPI）to obtain the perovskite precursor solution of Cd_xSn_（1-x）S-MAPI.Thereby,a hole-transport-layer-free PSCs structure of FTO/Ti O₂/Cd_xSn_（1-x）S-MAPI/Carbon was constructed.A high crystal quality perovskite film with larger crystal grains can be prepared by altering the doping ratio of Cd²⁺:Sn²⁺,which can improve the electron extraction capacity of the electron transport layer/perovskite interface,reduce the charge recombination at the interface,and improve the photoelectric performance of the cells.The results showed that the photoelectric conversion efficiency（PCE）of PSCs,preparing by adding Cd S,is 2.79%.While the PCE of PSCs prepared by adding Cd_xSn_（1-x）S（x=0.50）alloy is 5.84%,which is an increase of approximately52%,achieving the optimization of photovoltaic performance.（3）The studies on SnS quantum dots（QDs）sensitized MAPb_1-xSn_xI₃solar cells.To further improve the PCE of the device,in this chapter,we introduce Sn I₂into a single-component perovskite film MAPI anduse SnS QDs to sensitize the Pb-Sn two-component perovskite.The multi-component perovskite film SnS QDs-MAPb_1-xSn_xI₃ were prepared by a one-step solvent method.The results showed that the introduction of Sn I₂adding into the MAPI precursor solution can control the crystallization process of the perovskite solution,improve the crystallization quality of the perovskite,reduce the perovskite crystal defects,and thereby reduce the total carrier recombination loss of the device.The PCE of PSCs without Sn I₂was 7.68%,while that of PSCs with doping Sn²⁺（x=8%）reacheed11.94%,and a fill factor（FF）of 66%was obtained.The results showed that the advantages of different ion doping can be fully utilized to obtain the perovskite films with fewer defects and higher quality by altering the doping ratio of Pb²⁺:Sn²⁺.