Influence Of ZnO Nanorod Arrays Modification On The Photoelectric Properties Of CsPbBr₃ Perovskite Solar Cells And Its Mechanism

Since the first report of organic-inorganic hybrid metal halide perovskite solar cells(PSCs)in 2009,their power conversion efficiency(PCE)has increased rapidly,from the initial 3.8%to the current 25.7%,which is comparable to that of the commercial crystalline silicon solar cells,showing great potential applications.However,due to the volatility of organic components in organic-inorganic hybrid PSCs,perovskite materials will be affected by environmental factors such as light,humidity,temperature,etc.,and their phases are unstable,which affects their commercial development.In this context,all-inorganic PSCs have come into the field of researchers,among which CsPbBr3 perovskite has the best hygrothermal stability.In this paper,ZnO nanorod arrays were proposed for the electron transport layer(ETL)of CsPbBr3 PSCs,and the effect and mechanism of the modification of ZnO nanorod arrays on the optoelectronic properties of the device were studied.The main research contents are as follows:(1)To solve the issue of the open-circuit voltage loss,which usually occurs in the direct contact between F doped SnO2(FTO)conductive glass and CsPbBr3 perovskite light absorbing layer,a seed layer of SnO2 for growing ZnO nanorod arrays was deposited by a SnCl2 solution with anhydrous ethanol as solvent.In order to obtain the optimal electrochemical deposition time of ZnO nanorod arrays in the presence of SnO2 seed layer,several sets of comparative experiments were set up.Determined by the best photovoltaic performance of the device with PCE of 3.63%,the optimal deposition time was 15 min.(2)By examining the surface morphology of SnO2 seed layers at different annealing temperatures and the photovoltaic performance of the devices,the optimal annealing temperature was determined at 350℃.The corresponding device showed the the best overall performance,with open circuit voltage(Voc)of 1.18 V,short circuit current density(Jsc)of 5.96 mA/cm2,filling factor(FF)of 63.1%,and PCE of 4.44%.(3)The ZnO nanorod arrays/CsPbBr3perovskite interface is prone to charge recombination centers.In order to solve this problem,the surface of the ZnO nanorod arrays was deposited by SnO2 thin films for passivation.The effect of SnO2 passivation layer on the morphology of SnO2 coated ZnO nanorod arrays and the photovoltaic performance of CsPbBr3 PSCs at different annealing temperatures were explored.Through comparative analysis,it was found that the optimal annealing temperature was 350℃,and the PCE reached 4.60%.(4)Since the electrons generated by the CsPbBr3 perovskite light absorption layer cannot transport to the external circuit efficiently,ZnO nanorod arrays by Al3+ doping were used as the ETLs of CsPbBr3 PSCs.The influence of Al3+ doping concentration on the morphology,UVvis absorption spectrum,and energy band structure of ZnO nanorod arrays,as well as on the charge transfer and photovoltaic performance of the devices were investigated.It was confirmed that when the Al3+ doping concentration was 1 at%,the energy levels between the ZnO nanorod arrays and the CsPbBr3 perovskite layer were the best matched,and the light absorption ability was also the strongest.The Voc,Jsc,FF,and PCE of the device was 1.38V,6.83 mA/cm2,64.8%,6.09%,respectively.When the unpackaged device was stored in air atmosphere at room temperature for 60 days,the PCE still retained 90%of the initial value.