Improving The Stability Of CsPbI₂Br Perovskite Solar Cells With Additives

Perovskite solar cells have attracted much attention due to their low cost and high power conversion efficiency.Up-to-date,the best certificated efficiency of perovskite solar cells has reached 24.2%.However,perovskite material based on CH₃NH₃PbI₃ has poor thermal,light,humidity and oxygen stability,which seriously hinders the commercialization of perovskite solar cells.Among inorganic perovskite,cubic phase?-CsPbI₃?E_g¹.72 eV?is the most ideal optical capture material.However,it is easy to change from perovskite phase to non-perovskite phase at low temperature.Cesium-lead mixed halide perovskite CsPbI₂Br?E_g¹.92 eV?has attracted more attention due to its comprehensive consideration of band gap and phase stability.Reducing annealing temperature of inorganic perovskite by adding additive has proved to be an effective method.In this paper,the effect of three series of additives on the nucleation of CsPbI₂Br films was investigated.The performance of all-inorganic perovskite solar cells was improved by adjusting the doping concentration.Detailed research contents are as follows:First,research work by using iodine-containing ion additives?HI and LiI?to improve and stabilize the morphology of CsPbI₂Br cubic phase was studied.The CsPbI₂Br perovskite thin films and corresponding inverted planar devices were characterized by means of SEM,XRD,UV-vis,PL,TRPL,AFM,CA and EIS.The results showed that a best PCE of 6.1%for CsPbI₂Br-based device was obtained when 2 vol%HI was added?Jsc=12.51 mA/cm²,Voc=1.03 V,FF=47%?.At the same time,the device doped with 2 wt%LiI also exhibited good device performance?PCE=5.5%,Jsc=13.09 mA/cm²,Voc=0.76 V,FF=55.4%?.The device doped with LiI has higher Jsc due to the movement of Li ions.On this basis,the CsPbI₂Br perovskite device prepared by co-doping 1 vol%HI with 2 wt%LiI shows an improved PCE of 6.7%?Jsc=13.47 mA/cm²,Voc=0.95 V,FF=52.3%?.The stability test shows that the performance degradation of the co-doped device is less than 17%after 60 days storage in argon glove box.Second,the effect of two kind of indium-containing additives?In?C₂H₃O₂?₃ and InCl₃?on the morphology of CsPbI₂Br film and the performance of inverted planar device was investigated.Several testing methods including SEM,XRD,UV-vis,PL,TRPL,AFM,XPS,EIS were used.The results show that CsPbI₂Br film with uniform grain size and low grain boundary density can be prepared by doping indium-containing additives.The optimum efficiency of device doped with 0.25 wt%In?C₂H₃O₂?₃ can reach 5.3%?Jsc=11.17 mA/cm²,Voc=0.84 V,FF=56.6%?.The device doped with InCl₃ additive shows a better crystallinity and lower internal resistance than those doped with In?C₂H₃O₂?₃.When doped with 0.8 wt%InCl₃,the optimal device performance is obtained with Jsc of 12.82 mA/cm²,Voc of 0.82 V,FF of 55.5%,PCE of 5.8%.The PCE of the device with indium-containing additive just slowly decayed to 90%of its initial value,as the storage time increased to 35 days in argon glove box.Third,the effect of organic complex additive?Spermidine Trihydrochloride,STCl?on the morphology of CsPbI₂Br film and the performance of inverted planar device was investigated.Testing methods including SEM,XRD,UV-vis,PL,TRPL,AFM,CA were performed.The results show that the terminal R-NH₃⁺groups can complex with PbI₂ and effectively reduce the grain boundary defects,the adjacent crystal surfaces can be connected to achieve the purpose of stabilizing the lattice structure.When doped with 0.4 wt%STCl,the optimum device shows a best performance?Jsc=10.71 mA/cm²,Voc=1.01 V,FF=50.8%,PCE=5.5%?.The efficiency of the unpackaged device decreased to 76%of the initial efficiency after 35 days storage in argon glove box,which shows improved stability.