Defect Passivation For Organic-inorganic Hybrid Perovskite Solar Cells

With the rapid development of social and economy,the demand for energy increases significantly.Among the renewable and clean energy sources,such as hydro energy,geothermal energy,solar energy,wind energy,tidal energy and so on,solar energy possesses many unique advantages.Perovskite solar cells（PVSCs）,a rising star in the next generation,have greatly improved their power conversion efficiency（PCE）from 3.8%to25.7%,showing great commercialization prospects.Organic/inorganic hybrid PVSC have attracted widespread attention due to the excellent optoelectronic properties and processability of organic and inorganic materials,high PCE,and relatively low fabrication cost.In order to achieve high–performance PVSCs,researchers have made a lot of efforts in designing new device structures,manipulating interface morphology,exploring new perovskite materials,and controlling perovskite crystal growth.In addition,the growth of perovskite crystals is related to the morphology of perovskite.Anti-solvents,bulk organic components,thermal substrate casting,and additives have all been used to improve perovskite crystal growth.Among them,nucleation and crystal growth can be well controlled by adding additives that are expected to reduce charge recombination.The additive,through their functional groups,can form a powerful chemical bond with perovskite,and occupy the interstitial site,thereby suppressing the formation and immobilization ions of defects,resulting in enhanced efficiency and stability.Therefore,this thesis conducts related research on the defect passivation of different kinds of additives in the perovskite functional layer.The main contents are as follows:（1）By introducing PAB,a polyamide derivative,into the perovskite precursor solution,we investigated how three passivating functional groups of PAB（hydroxyl,carboxyl,and amine groups）act together on the perovskite photoactive layer and influence the performance of its devices.PAB makes the perovskite grain size smaller,the surface becomes smoother,and the defects and voids are correspondingly reduced to obtain a high-quality film,which can separate photogenerated carriers more effectively and enhance the device performance of PVSCs.The PCE of PAB-0.15 device can reach 21.13%,which is higher than 19.42%of the control device.At the same time,the stability of the device has also been improved.The PCE of PAB-0.15 device can still maintain 95%of its original PCE at room temperature with a humidity of 50%for 32 days.PCE of the control device only retained 82%of its original PCE.（2）PVSCs with ITO/Sn O₂/perovskite/PDTT-T/Mo O₃/Ag device structure were investigated by adding the ionic liquid BDMIMBF₄ to the perovskite precursor solution,with BMIMBF₄ as the reference.After BDMIMBF₄ was doped into the perovskite precursor solution,the grain sizes of the perovskite films were larger than the grain sizes of the original perovskite doped with BMIMBF₄ and the original perovskite.At the same time,the carrier transport efficiency is further improved,the electron-hole pair complex is reduced.The doped perovskite film has better crystallinity,larger grains as well as fewer grain boundary defects,ultimately improving device performances of PVSCs.PCE of the devices based on BMIMBF₄ doping can come up to 19.37%,and PCE of the PVSCs based on BDMIMBF₄doping can come up to 20.29%,which was higher than the control device of 18.96%.At the same time,PCE of the device doped with BDMIMBF₄ can still maintain97%of its original PCE after 30 days of storage at room temperature with a humidity of50%,which is higher than that of BMIMBF₄（86%of its original PCE）and the control device（80%of its original PCE）.（3）Adding tetraphenylphosphonium chloride to the perovskite precursor solution,the crystallinity of photoactive layer is effectively improved and the grain size is increased.Therefore,the surface morphology of the film is improved,further improve the carrier transport efficiency and reduce the carrier complex.The carrier extraction efficiency is beneficial to reduce the non-radiative loss inside the device,so that the device performances of PVSC can be significantly improved.By improving the doping ratio of tetraphenyl chloride,PCE of the tetraphenylphosphonium chloride based 5%doped perovskite devices was 20.15%,which was higher than that of the control devices（17.61%）.At the same time,PCE of the tetraphenylphosphonium chloride based 5%doped device can still maintain 94%of its original PCE after 30 days of storage at room temperature with a humidity of 50%,which is higher than that of the control device.