Interface Engineering And Grain Growth Tunning With Zwitterionic Compounds For Perovskite Solar Cells

Due to the merits of solution-processability,low fabrication cost and high power conversion efficiency(PCE),perovskite solar cells have attracted more and more attention.The certification efficiency has reached 25.2%,which is comparable to silicon-based solar cells.To prepare high-performance perovskite solar cells,perovskite active layers should possess excellent charge separation capabilities and photoelectric conversion performance.Besides,the charge transport layers,which affect the charge transport and the optimization of the perovskite active layer,plays a vital role in improving the performance and stability of devices.This thesis mainly studied the effect of application of sulfobetaine methacrylate(SBMA)and its polymer PSBMA in p-i-n perovskite solar cells.PSBMA and SBMA were used as interface layers and the additive of active layer,respectively,thereby improving the morphology and quality of the active layer,and reducing the energy level barrier between the transmission layer and the electrode,aiming to obtain high efficient and stable perovskite solar cells.The details are as follows:1.The zwitterionic polymer PSBMA was applied to modify the hole transport layer and the electron transport layer.(1)PSBMA was used to modify the hole transport layer PTAA.Because of the hydrophilicity of the zwitterionic group,the wettability of the perovskite precursor solution on the hole transport layer had been improved.Thus,dense perovskite films with fewer pin holes were attained,which reduced the density of defect states and improved the open circuit voltage.In addition,the coverage of the perovskite film improved,which made it easier to fabricate large-area devices.(2)PSBMA was used to modify the electron transport layer PC6iBM.The surface dipoles generated by the PSBMA zwitterionic group reduced the work function of the cathode A1 and the energy level barrier between PC61BM and Al,which improved the electron injection efficiency.(3)PSBMA was used to modify both PTAA and PC61BM.Finally,the PCE was improved from 17.31%to 19.16%and the device stability was also improved.In addition,a PCE of 15.7%was achieved for large-area device with area of 1 cm2.2.The zwitterionic monomer SBMA was used as a dopant for the perovskite layer.The C=O and S=O groups in SBMA can form Lewis acid-base pairs with Pb2+,which controlled the growth of perovskite crystals and obtained perovskite films with fewer pin holes and higher quality,thereby reducing the density of defect states and improving the open circuit voltage and fill factor.The PCE of perovskite solar cells increased from 19.77%to 21.44%.More importantly,the thermal stability of the device had been greatly improved.After being heated in nitrogen at 60? for more than 300 hours,the efficiency of the device can still maintain more than 90%.