Modification Of MA-based Perovskite Light Absorption Layer And Study On Solar Cell Performance

Organic-inorganic hybrid perovskite has attracted wide attention in the photovoltaic field due to its excellent photoelectric properties,and is considered as the most potential material for the next generation photovoltaic devices.Perovskite solar cells（PSCs）have achieved incredible rapid progress in the past few years,but the commercialization of PSCs still faces many challenges,such as solvent and material toxicity,poor stability,and so on.As the core photoactive layer of perovskite solar cells,the quality of perovskite thin films is an important factor affecting the photoelectric performance and stability of PSCs.Therefore,this study took the preparation of high-quality perovskite thin films as the starting point to conduct the following investigations.The specific research is as follows:Aiming at the toxic antisolvent in the one-step antisolvent method,environmentally friendly ethyl acetate（EA）was used as the anti-solvent to prepare perovskite films in the atmospheric environment.Combined with DFT calculation and experimental results,it is shown that the interaction between the EA and the DMSO can improve perovskite crystallization,forming high-quality perovskite films with larger grain size and smoother surface.Based on the perovskite films,we fabricated planar PSCs,the highest power conversion efficiency（PCE）of the corresponding device is 17.83%.MAPbI₃ films have been successfully prepared using EA green anti-solvent in the atmospheric environment.In view of the factors affecting the stability of the perovskite structure,FA/MA mixed cation-based perovskite films are prepared.Through the study of film morphology and corresponding device performance,we find the dense perovskite films with the preferential crystal orientation and low trap-state density can be obtained,when 30%of FA⁺is incorporated into MAPbI₃.As a result,the corresponding PSCs devices are fabricated with the mixed cation-based perovskite films,achieving a champion PCE of 19.50%.In addition,the mechanism of stability improvement of FA/MA mixed cationic perovskite was revealed by DFT calculation.MAPbI₃ films have been successfully prepared using EA green anti-solvent,But the polycrystalline films and the soft ionic properties make perovskite films have various defects.Herein,taking passivation defects as the entry point,sodium dodecylbenzenesulfonate（SDBS）are introduced into the MAPbI₃ perovskite precursor solution.It was found that the introduction of SDBS can slow down the crystallization rate,which favors highly preferred crystal structure.The coordination between SO3^-and Pb²⁺,the interaction between sodium ion（Na⁺）and I^-not only reducing induced deep level traps,but also preventing iodine migration.As a result,the corresponding PSC device outputs a champion PCE of 19.20%and exhibits improved stability.Aiming at the charging characteristics of defects in perovskite materials,Lewis acid-base additives have attracted the attention of researchers due to the targeted coordination with unwanted defects.Here,1H-benzimidazole（BIZ）is employed as a zwitterion Lewis acid-base additive in perovskite precursor In-depth theoretical calculations and experimental characterizations reveal the dual-site synergistic passivation of BIZ,and the conjugated structure of benzene ring tends to increase the interaction between BIZ and perovskite.Thus,uniform and dense perovskite films are achieved,with large grain size,few grain boundaries,enhanced crystallinity,and low defect density.Consequently,the target PSCs devices based these films achieve a champion PCE of 24.59%andexcellent stability.The unencapsulated PSC maintains 91.49%of original PCE after storing in air with an average relative humidity（RH）of 40%for 2400 h.Moreover,the device exhibits remarkable the long-term operational stability,maintaining 90.47%of initial PCE after continuously operating at the maximum power point for 1000 h.Furthermore,to demonstrate the universality of BIZ passivation,perovskite solar module（27.5cm²）are also fabricated,and a PCE of 20.49%was achieved.The residual strain of the perovskite film seriously affects the stability of the film and the corresponding device.Therefore,for the intrinsic instability of the perovskite film,a negative thermal expansion material（NTE）is introduced to achieve stress relaxation.NTE can not only serve as a soft template to assist the growth of high-quality perovskite films,but also compensate the high thermal expansion coefficient（CTE）of perovskite films due to its negative thermal expansion characteristics,reducing the CTE mismatch between the perovskite and the substrate.To a certain extent,the residual tensile strain of the perovskite film is effectively relaxed to 32%of that of the reference film,PSCs devices with a PCE of 22.40%are fabricated in the atmospheric environment while improving the film stability.