The Study On Stability And Interface Characteristic Of CsPbI_3-xBr_x Perovskite Solar Cells

All-inorganic perovskite solar cells have attracted great attention due to their excellent optical and electrical property.Compared with organic-inorganic hybrid perovskite,all-inorganic perovskites has the advantages of high quantum yield,adjustable band gap,good thermal stability and is the first preferred materials for perovskite solar cells.Currently,the efficiency of inorganic perovskite solar cells has exceeded 18%.This paper mainly studies the stability,interface defects and ways to improve efficiency of all-inorganic perovskite cells.The contents are as follows:1.Using the Spiro-OMTAD hole transport layer to take place of the P3HT hole transport layer to reduce the interface defect between the CsPb I_3-xBr_x perovskite film and hole transport layer,which improved the extraction capacity of the hole transport layer for carriers and increased the light and thermal stability of the device.In the experiment,an all-inorganic perovskite solar cell with ITO/LiF/SnO₂/CsPbI_3-xBr_x/P3HT/Au structure was designed.The open circuit voltage(V_oc)of the best device is 1.12V,the short-circuit current density(J_sc)is 18.43 mA/cm²,the fill factor（FF）is 76.96%and the power conversion efficiency（PCE）is 15.84%.The results showed that P3HT effectively suppressed the recombination of carriers between the CsPb I_3-xbr_x perovskite film and the hole transport layer at the interface,which reduced optical energy loss and decreased the defect state density of the CsPb I_3-xbr_x perovskite film.In addition,the device exhibited high light and thermal stability,which can maintain about 80%of the initial PCE during 280hours of irradiation.The device heated in nitrogen glove box under 85°C for 80 hours can maintain 90%of the original efficiency.2.The PCE of the CsPbI₂Br perovskite solar cell was increased by adding excessive amounts of PbI₂ and Cs I,and finally a PCE of 11.8%was obtained,which was 2%higher than control device.The V_occ of the device is 1.19V,J_sc is 15.19mA/cm²and FF is 65.41%.In addition,the annealing temperature of the CsPbI₂Br perovskite solar cells was optimized,and the 260℃to be found was the best annealing temperature for the CsPbI₂Br perovskite cell.The V_oc is 1.2V,J_sc is 15.47m A/cm²,FF is 71.6%and the highest efficiency is 13.34%of the device,which behaves good light stability maintaining 85%of the initial efficiency under 300 hours of continuous lighting.3.The thermal stability and efficiency of CsPb I₃ perovskite solar cells were improved byco-doping of In³⁺and Rb⁺ions.After about 50 hours of continuous heating under 80℃,thethermal stability of the device doped with 2%In³⁺and 5%Rb⁺ions was slightly better than undoped device and can maintain 70%of the original efficiency.However,the undoped device only maintained 50%of the initial efficiency.The V_oc of the optimal device is1.01V,J_sc is 18.72mA/cm²,FF is 75.08%and PCE is14.19%.Compared with the undoped device,the hysteresis effect was significantly reduced,and the difference between forward and reverse scann was within 0.5%.Secondly,the morphology of the perovskite film becomed better.Compared with the surface morphology of the undoped device and the perovskite film doped with 2%In³⁺and 5%Rb⁺ions,the morphology of the undoped device was inferior to the perovskite film doped with 2%In³⁺and 5%Rb⁺ions.Once again,the photoluminescence and transient photoluminescence spectroscopy confirmed that the non-radiative recombination in the perovskite film was also reduced.Finally,compared with the undoped perovskite film,the film doped with 2%In³⁺and 5%Rb⁺ions showd higher crystallinity by X-ray diffraction（XRD）.