Inorganic CsPbI₂Br Solar Cells Research On Composition Regulation And Transport Layer Optimization

Metal halide perovskite materials have attracted close attention due to their excellent photoelectric properties,low exciton binding energy and low production cost.So far,the highest photoelectric conversion efficiency of perovskite solar cells has reached 25.8%,which is close to silicon solar cells.Among them,all inorganic CsPbI₂Br perovskite has become a research hotspot in the field of perovskite because of its excellent film thermal stability and suitable band gap.In this paper,the negative effects of traditional environmental oxidation on CsPbI₂Br devices were avoided by pre-oxidizing Spiro-OMe TAD hole transport layer,and the efficiency performance and stability of all inorganic CsPbI₂Br perovskite solar cell devices were improved by using the strategy of solution component regulation of perovskite precursor.A new direction is proposed for the construction of p-n junction cell.The main conclusions are as follows:The effects of two pre-oxidation motheds of Spiro-OMe TAD on CsPbI₂Br were studied and explored.The pre-doping of Spiro-OMe TAD was realized effectively by preoxidation of O₂ or CO₂.O₂ preoxidation mothed could increase the photoelectric conversion efficiency of CsPbI₂Br device from 8.30%to 11.63%,and the V_oc from 1.00V to 1.23 V.However,the humidity of introduced air was not controllable,resulting in poor controllability of the pre-oxidation process.CO₂ preoxidation method was used to inject CO₂ gas into Spiro-OMe TAD solution with UV irradiation.Compared with O₂preoxidation,the Spiro-OMe TAD film obtained by CO₂ preoxidation has stronger hole extraction ability and lower interfacial transmission impedance,and its cell device achieved 10.19%efficiency and this preoxidation method has good experimental repeatability.The influence of CsPbI₂Br self-doping on the conductivity of the thin film was studied.By regulating the component ratio of CsPbI₂Br precursor solution,it was found that the introduction of excess Pb I₂ or shortage of Cs I might lead to the transformation of the conductive type of the thin film to n-type,which might help to improve the open-circuit voltage of the CsPbI₂Br device,and thus improve the photoelectric conversion performance of the whole device.When excess Pb I₂ was added into the precursor solution of CsPbI₂Br,the photoelectric conversion efficiency of the cell was increased from 8.30%to 9.94%,and a high V_oc of 1.25 V was achieved,with an average voltage of 1.21 V.A higher V_oc of 1.17 V was also achieved by reducing the amount of Cs I in the precursor solution.It was found that introducing excessive Pb or reducing the content of I might lead to certain passivation effect on the defects in the film,thus improving the conversion efficiency of the battery.The photoelectric conversion efficiency of Cs Pb_1.06I₂Br could be improved from 8.69%to 10.09%,and the average V_oc was increased to 1.21V.When the content of I was absent,the density of carrier traps and defect states of perovskite films could be effectively reduced,and the conversion of photoelectric efficiency was significantly improved.The efficiency of CsPbI_1.94Br was also improved to 9.45%.After being placed in 15%humidity environment for more than 50 hours,the initial photoelectric conversion efficiency of CsPbI_1.94Br can still maintain 65%,while the CsPbI₂Br can only maintain 39%of its initial photoelectric conversion efficiency.