Application Of Tin Dioxide Electron Transport Layer In Perovskite Solar Cells

Organic-inorganic hybrid perovskite solar cells?PSCs?have dramatically revolutionized the photovoltaic research.Electron transfer layer?ETL?is one of the key components in high performance PSCs,but the traditional Ti O₂-ETL is hard to meet the increasing demand of high stability,low cost,easy preparation and flexible application of PSCs.In this paper,we designed a new Sn O₂-Ti O₂ synergistic ETL to resolve the problems of unfavorable electron transport of Ti O₂ double-layer structure ETL,and the high electron mobility and high defect state contradiction of Sn O₂ material.For the difficult preparation of high quality Sn O₂ nanocrystalline ETL at low temperature,we designed a new sol-gel method and made a substrate surface moisture controled in situ crystalline regrowth for improved crystallinity.The main research contents are as follows:?1?By adjusting the amount of Sn O₂ in the ETL,a new type of Sn O₂-Ti O₂synergistic ETL was designed and related divice photovoltaic property was further studied.In the new synergistic ETL,the low conductive compact Ti O₂ layer was successfully removed,and the contradiction between the high mobility and the high defect state of Sn O₂ was resolved.Finally,the Sn O₂ underlayer and the Ti O₂ mesoporous layer synergistic with each other to promote the electron transmission,suppress the interface charge recombination,thus improve the efficiency?from 17.27%to 18.16%?and stability of the full device.?2?The Sn O₂ nanocrystalline electron transport layer were preparated at low temperature?<80°C?.During the sol-gel process,a trace of water vapor in the air was introduced into the reaction system by using opened reflux method to control the hydrolysis reaction of Sn ions,and open up a low energy barrier crystallization path.Under the temperature of less than 80°C,the Sn O₂ nanocrystalline with diameter of 2-3nm were fabricated,and the ETL based on this Sn O₂ nanocrystallinen needn't further high temperature?>100°C?treatment.Its high conductivity,transmittance and proper conduction band position endow the high PCE of 19.2%and 16.1%for rigid and flexible PSCs,respectively.Moreover,the wide bandgap??4.1 e V?of Sn O₂-ETL has given a better UV light stability than the high temperature Ti O₂-based devices.?3?The high-quality Sn O₂-ETL based on substrate surface water-induced nanocrystal in situ regrowth and related PSCs photovoltaic properties of were studied.A trace amount of moisture on FTO substrate surface was controlled by ultraviolet ozone pretreatment.The trace moisture then induced the in situ regrowth of Sn O₂ nanocrystals during film formation at room temperature.This new approach results in full-coverage Sn O₂ ETL with a desirable morphology and crystallinity for superior optical and electrical properties,as compared to the control Sn O₂ ETL without the UVO pretreatment.Finally,the rigid and flexible PSC devices based on our new Sn O₂ ETLs yield high PCEs of up to 20.5%and 17.5%,respectively.