Growth Mechanism Study Of Perovskite Thin Film And Its Application In Photovoltaic Cells

Since the report of solar-to-electricity conversion in 2009,the organic-inorganic perovskite solar cell structure has undergone four stages of sensitized structure,mesoporous structure,columnar structure and planar heterojunction structure.Its power conversion efficiency has also dramatically increased from the initial 3.8%to 22.6%.The increase in performance is mainly due to the optimized composition and interfacial material in contact with the perovskite.All experiments in this paper are based on the planar inversion structure of PEDOT:PSS,because it could use a full solution method which is not only simple but also suitable for flexible substrates at low temperatures.However,so far the power conversion efficiency using planar inverse structure is generally lower than the mesoporous structure.Therefore,we hope to improve the performance of planar inverse perovskite solar cell with PEDOT:PSS structure by exploring the dynamic crystallization of perovskite film and optimizing the two-step solution spin-coating method.The main contents are as follows:1)To optimize the traditional two-step spin-coating solution method that based on planar inverse structure,we added an appropriate amount of polar solvent DMF to the MAI precursor solution to control the rate of perovskite crystallization and solved the problem of remaining lead iodide.The average power conversion efficiency?PCE?of the device is more than 15%,the open-circuit voltage(V_OC)reaches 0.98¹.01V,the short-circuit current density(J_SC)reaches 20²2 mA/cm²,the fill factor FF is 77%⁸0%.2)Based on the improved two-step spin-coating method,we optimized the amount of polar solvent additive DMF and determined that the device prepared by adding 0.9%vol DMF to MAI precursor solution has the best performance and the best stability.3)We explored the band gap modulation of FA doping.Based on the improved two-step spin-coating method for preparing perovskite film,we found that FA doping could effectively enhance the light absorption of the material in the near infrared region.The experimental results further confirmed that when the ratio of MAI/FAI precursor solution is 7:3,the device prepared has the best efficiency,PCE reaches 17.2%,V_OC is 0.92V,J_SC is23.7 mA/cm² and FF is 78.9%.