Research On Fabricating Large Size Perovskite Solar Cells Using Sequential Deposition Method

As the energy crisis and environmental problems are highlighted,the demand forclean and renewable energy is increasing,and the energy supply principals are undergoing revolutionary changes.Solar cell has become one of the research hotspots in the field of energy.In recent years,the organic/inorganic hybrid perovskite solar cell has the characteristics of high efficiency,simple processes and low costs,which is becoming a future star in this field.In this paper,preparation technologies of the perovskite solar cell are studied.Based on these techniques,large size perovskite solar cells on both flexible substrates and rigid substrates are fabricated.Also,the devices stability is tested and a solution was used to improve the device stability.The following include the main research contents and conclusions.First,the evaporation/spin coating method was used to prepare the perovskite layer of the solar cell.The influence of rate-controlled evaporated PbI₂ films on the quality of perovskite layer and final performance of planar structured perovskite solar cells is investigated.An ultrafast evaporating rate of 20?s^-1 was found to be benefit to the conversion from PbI₂ to CH₃NH₃PbI₃ perovskite.The power conversion efficiency（PCE）of the device reached 14.88%,which shows a hysteresis free perovskite solar cell.Secondly,Large area pinhole free CH₃NH₃PbI₃ perovskite thin films were successfully fabricated through the sequential evaporation/spin-coating deposition method on 5 cm×5 cm flexible indium doped tin oxide coated polyethylene naphthalate（ITO-PEN）substrates in this research.Based on these high quality CH₃NH₃PbI₃ film,the resultant flexible perovskite solar sub-module（active area 16 cm²）with power conversion efficiency of more than 8%and a 1.2 cm² flexible perovskite solar cell with power conversion efficiency of 12.7%were obtained,respectively.The bending stability was tested and the failure factors of bending were analyzed.Then,the deposition process of the perovskite absorber was optimized,and the size of the device was enlarged to 10 cm×10 cm.we adopted the volume expansion routine to scale-up from a 0.16 cm² laboratory-scale devices to large size perovskite solar module（PSM）with a PCE loss of 8%and reached a certified PCE of 13.98%.The PCEs of the PSM with Au electrode dropped to 38%of the initial efficiencyafter 16 days’storage,which is quite different from efficiency of PSCs retaining more than 90%of the initial after 40 days’storage.However,the efficiency of PSM with Cu as counter electrode retained 90%of the initial value after 30 days’storage,which greatly improved the stability of PSMs.We also introduced hot spots heating（HSH）characterization method to investigate the stability of PSM.HSH reveals that Cu electrode can greatly reduce numbers of hot spots and extent of temperature increase in a PSM compared with Au electrode.Although both Au and Cu diffuse into Spiro-OMeTAD layer,Au keeps in the metallic form which may act as shunting path and detrimental to device photovoltaic performance.In contrast,Cu is oxidized to Cu⁺which is likely in the form as CuI and electronically benign.This study also found that PSCs with stable material component and devices structure could work for a long time,while it was not suitable for large size PSMs.Thus,this work provides a new idea toward fabricating the low-cost perovskite solar modules for commercial applications.