Research On Light-induced Degradation Of Methylammonium Lead Iodide Perovskite

Recently perovskite(PVSK)solar cells(PSCs),which are based on organic-inorganic metal halide PVSK,have gained much attention due to their extraordinary optical and electrical properties in photovoltaic(PV)area.Compared with inorganic solar cells based on Si,perovskite materials are cheap and easy to prepare,which make PSCs competitive;Also PSCs have achieved high power conversion efficiencies(PCE)of 22.1%,surpassing the well-studied organic photovoltaics(OPV).However,organic-inorganic perovskites tend to degrade under many conditions,such as illumination,high temperature,bias,moisture,oxygen and high-energy irradiation.The reported lifetimes of PSCs are less than 2000 h,while commercially silicon solar cells maintain over 85%of their initial efficiency over a course of 25 years.Thus,achieving stable organic-inorganic perovskite solar cells is key to a successful commercialization.However,the degradation mechanisms in general and light-induced processes in particular are still unknown.As a result,the fundamental research of light-induced degradation is extremely urgent in order to provide a guidance for better device design.(1)At first,we investigated several factors which affected the film morphology and crystal structure,including the type of anti-solvent,dripping timing,spinning rate and annealing temperature.The results implied that the perovskite precursor solution spin coated with 1 500 rpm for 10 seconds and then spin coated with 3 000 rpm for 35 seconds with chlorobenzene dripped,following by 20 minutes annealing at 100° will form the best film morphology.We also found that dripping time of the anti-solvent and spinning rate are key factors forming homogeneous and uniform film.(2)Then we conducted research on light-induced degradation of MAPbI3 perovskite.Two conditions were chosen:ultra-high vacuum(UHV)and inert atmosphere.The results showed that the degradation rate was faster in UHV than in an inert atmosphere,which definitely lead to strong destruction of the electronic structure,surface morphology and surface components.Besides,we made several measurements to explore the degradation mechanism.Whatever,it is verified that the perovskite material is light-sensitive and the degradation process will have a significant impact on the device stability and long-term performance.