Study On The Preparation And Property Of SnO₂-based Perovskite Solar Cells Modified With Potassium Thiocyanate

In 2009,organic-inorganic hybrid metal halide perovskite materials were first applied in the field of solar cells.Today,the efficiency of perovskite solar cells has exceeded 25% with broad application prospects.For the selection of the electron transport layer in perovskite solar cells,SnO₂ has high photoelectric characteristics and easy fabricates at low temperatures,therefore have been widely used.However,there are certain interface defects between SnO₂ and the light-absorbing layer.In this paper,the pseudo-halogen salt potassium thiocyanate（KSCN）was introduced into SnO₂ to assemble the cells and study the photoelectric performance of the device.The experimental results show that KSCN helps SnO₂ to form a denser and smoother electron transport layer film,which is helpful for electron extraction and transport.The experimental results of three different compositions of perovskite materials were used to assemble cells based on SnO₂ and KSCN-SnO₂ show that the influence of KSCN-SnO₂ on the device’s photoelectric performance has nothing to do with the perovskite layer,and it has universal significance.At the same time,the mixing cation and anion perovskite materials can improve the photoelectric performance of the device.A high-quality FA0.5MA0.5Pb I2.8Br0.2 perovskite film was formed on the KSCN-SnO₂ substrate.The cells based on KSCN-SnO₂ presented higher performance,and its best device has an open circuit voltage of 1.04 V,current density of 20.84 m A·cm-2,fill factor of 76.69%,the highest efficiency of 16.78%,and the hysteresis index reduces to 0.1526 with better reproducibility that the average efficiency of the 20 pieces of cells based on KSCN-SnO₂ was 15.74%.According to the experimental result of photoelectric performance,the mechanism of the influence of SnO₂ introduced by KSCN on the photoelectric performance of the device was studied.It is easier to extract effective electrons from perovskite that the work function of the surface of the KSCN-SnO₂ electron transport layer was reduced from 4.81 e V to 4.50 e V.The defect state of the KSCN-SnO₂ electron transport layer/perovskite layer is effectively passivated to accelerate the charge carriers transfer process and reduce the hysteresis.Moreover,the corresponding optimized structure of SnO₂-KSCN|MAPb I3 was established and the electron distribution was calculated to illustrate the positive effect of KSCN-SnO₂ electron transport layer on the perovskite layer.