Preparation And Research Of PC₆₁BM Optimized Electron Transport Layer Flexible Perovskite Solar Cell

In this thesis,by tuning the annealing temperature of the dense TiO₂ layer from 500?to 150?and optimizing the low-temperature compact TiO₂ layer with PC₆₁BM,we fabricated planar heterojunction perovskite solar cells on flexible substrates successfully.The experiments specifically include the following four aspects:1.The optimal standing time after the process of the MAI precursor solution spin-coating was determined.We prepared and characterized three kinds of devices with different resting times?0 s,5 s and 10 s?before sintering process.The experiments data indicates that the performance of 0 s cell was best,which gives a PCE of 4.32%corresponding to a V_occ of 0.89 V,a J_scc of 11.77 mA/cm² and a FF of 40.99%.This result confirmed that the crystallization of the perovskite was basically completed during the spin process of the MAI precursor solution.The residual DMF?+DMSO?in the film could dissolve the as-formed MAPbI₃ grains in the long standing time before annealing,and the perovskite crystals became more small,uneven and malformation.The preparation method of the high-temperature compact TiO₂ layer was two-times spin-coating with two-times annealing,and the best efficiency of the cell reached 4.68%.The thickness of the compact layer was¹40 nm.2.The law-temperature compact TiO₂ layer was fabricated by spin-coating low-temperature nanocrystalline TiO₂ solution.The volatilization rate of the residual solvent in the compact TiO₂ film had a great influence on the morphology of the layer,and the annealing process seriously affected the volatilization rate of the solvent.In order to determine the optimal annealing process for the low-temperature dense layer,we designed three processes:direct annealing at 150?,the annealing temperature increased from 20?to 150?,and the annealing temperature increased from 20?to 150?after 1 h resting?1h process?.The 1 h-1time spin-coating layer showed less through holes and better coverage on FTO surface.The V_occ of the perovskite solar cell prepared on the ITO substrate based on this process was 0.92 V.3.The PC₆₁BM was used to solve the short-circuit problem caused by the holes of the law-temperature compact TiO₂ layer.The five different concentration of PC₆₁BM solution were used,which were 5,10,15,20 and 25 mg/mL.The optimum concentration on the FTO substrate was 15 mg/mL,corresponding to the V_occ of the device was 1.01 V,the J_scc was 14.74 mA/cm²,the FF was 36.70%,and PCE was 5.48%.One the other hand,the best concentration should be 20 mg/mL on the ITO rigid substrate,corresponding to the V_occ of the cell was 1.04 V,the J_scc was 17.11 mA/cm²,the FF rose to 46.53%,and the PCE was8.24%.The reverse and forward scan curves of the cells on both rigid substrates by the best concentrations showed extremely law hysteresis,demonstrating the good passivation effect of PC₆₁BM on the interface defects between the compact TiO₂ layer and the perovskite layer.4.The A-site and X-site doping perovskite solar cell was prepared using a mixed formamidinium-methylammonium-halogen(FA_xMA_1-x-x Br_xCl_yI_1-x-y)precursor solution.The perovskite film prepared by FA_xMA_1-xBr_xCl_yI_1-x-y-x-y precursor solution with the optimum concentration of 60:6:6 mg/mL was uniform and dense,and the average diameter of the grains was no less than 500 nm.The XRD patterns showed that the two precursor solutions reacted sufficiently at this concentration.With the minimal amount of PbI₂ remaining,the PCE of device was up to 9.79%.Based on the all optimal processes of this paper,a flexible planar heterojunction perovskite solar cell with a 3.24%PCE was achieved.