Novel Electron Transport Layer And Fullerene Derivatives Interface Modification Layer For Perovskite Solar Cells

Since methylamine lead iodine perovskite materials was introduced into the field of inorganic-organic solar cells in 2009,perovskite solar cells(PSCs)that use ABX3 type perovskite materials as the active layer have developed rapidly and have achieved remarkable achievements.Within eleven years,the power conversion efficiency of PSCs has rapidly increased from 3.8%to 25.5%.The perovskite material has a suitable band gap,a long carrier diffusion length,and a fast carrier mobility,so that when it is used in solar cells,the device can have a wider light absorption range and fewer carriers recombination.However,PSCs still have some shortcomings that cannot be ignored,which limit their industrial applications.For example,the large-area preparation process of PSCs still needs further exploration.Besides,the perovskite layer is unstable and decomposition will occur during long-term exposure to water,oxygen and light,so that the power conversion efficiency of PSCs will be greatly reduced.Moreover,PSCs also have a significant hysteresis effect.Relevant studies have shown that TiO2,which is an electron transport layer widely used in PSCs,is one of the main reasons for poor device stability.The low electron mobility of TiO2 and its photocatalytic effect lead to hysteresis and perovskite degradation at the interface.To address this problem,this article mainly focuses on the application of a new type of electron transport layer in PSCs and the passivation effects of fullerene modification layer:(1)For the first time,Sb2O3 was used as the electron transport layer(ETL)for Cs-FA-MA based PSCs.We have achieved the highest power conversion efficiency of 18.77%for Sb2O3 based PSCs.The solution-processed Sb2O3 was prepared under low temperature conditions.The Sb2O3 ETL has a suitable energy level and high electron mobility,which can be prepared by a simple spin coating process without high temperature sintering.PSCs based on Sb2O3 ETL have a high power conversion efficiency and relatively good repeatability,so that it may have great prospects in both rigid devices and flexible devices in the future.(2)Tetra-adducts and hexa-adducts of C60 with malonic acid were synthesized,which were used as the interface modification layer for PSCs.The 8-12 carboxyl functional groups attached on C60 through Bingle reaction and hydrolysis reaction greatly improve the solubility of fullerene derivatives in water and alcohol solvents.These carboxyl functional groups of fullerene derivatives play a role of interface modification and passivation,which can effectively modify the defects between the SnO2 ETL and the perovskite light-absorbing layer.As a consequence,PSCs modified by the fullerene derivatives achieved energy conversion efficiency over 20%with increased open-circuit voltage and fill factor.