Interface Modification by Ionic Liquid for Efficient and Stable FAPbI3 Perovskite Solar Cells
Formamidinium lead iodide(FAPbI3)perovskite solar cells(PSCs)have attracted significant attention owing to their outstanding optoelectronic properties,but long-term device stability is still a crucial issue related to FAPbI3 PSCs.FAPbI3 undergoes phase transition from black perovskite phase to yellow non-perovskite phase at room temperature,and moisture triggers this phase transition.One of the most widely used methods to improve the stability of PSCs is interface engineering.Being green functional solvents,ionic liquids(ILs)have been regarded as potential alternatives to toxic interface modifiers,thereby increasing their commercial viability and accelerating their adoption in the renewable energy market.In this study,an IL,1-ethyl-3-methylimidazolium tetrafluoroborate(EMIM[BF4])was used to modify the interface between the electron transport layer and perovskite layer due to its low volatility,low toxicity,high conductivity,and high thermal stability.The introduction of IL not only reduces interface defects but also improves perovskite film quality.Density functional theory(DFT)calculations show that there is a strong interface interaction between the IL and perovskite surface that is beneficial to decrease the density of defect states of the perovskite surface and stabilize the perovskite lattice.Apart from the defects in the perovskite film,solution-processed SnO2 also suffers from surface imperfections.Defects on the SnO2 surface generate defect states,which cause band alignment issues and stability issues.DFT calculations show that the surface gap states with IL are smaller than those without IL.Such weakened surface gap states indicate reduced carrier recombination at the surface region,which improves the device performance.Consequently,we achieved a power conversion efficiency exceeding 22%for the IL-modified FAPbI3 PSCs(control～21%).After storing for over 1800 h in a dry box(relative humidity(RH)～20%),the champion device retained～90%of its initial efficiency,while the control devices degraded into non-perovskite yellow hexagonal phase(δ-FAPbI3).
FAPbI3Phase stabilitySnO2Perovskite solar cellsIonic liquidInterface engineering
Yameen Ahmed、封想想、高远基、丁洋、龙操玉、Mustafa Haider、李恒月、李专、黄誓成、Makhsud I. Saidaminov、阳军亮
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中南大学物理与电子学院,超微结构与超快过程湖南省重点实验室,长沙 410083
Department of Electrical & Computer Engineering,University of Victoria,3800 Finnerty Road,Victoria,British Columbia V8P 5C2,Canada
中南大学粉末冶金国家重点实验室,长沙 410083
广西晶联光电材料有限公司,广西 柳州 545036
中南大学材料科学与工程学院,长沙 410083
Department of Chemistry,University of Victoria,3800 Finnerty Road,Victoria,British Columbia V8P 5C2,Canada
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