Study Of Hole Transport Layer And Photovoltaic Performance Of Cesium-lead Halogen Perovskite Solar Cells

Lead halide perovskites are currently a class of hot materials with significant growth potential in the field of solar cells and have the advantages of high carrier mobility,large light absorption coefficient,adjustable optical band gap,simple preparation process,etc.The efficiency of solar cells based on organic-inorganic hybrid lead halide perovskites has exceeded 25%;however,the problem of poor thermal stability has not been resolved,which has seriously affected its commercial application process.Although,by replacing organic component with cesium ions in the organic-inorganic hybrid perovskite,the all-inorganic cesium lead halide perovskites exhibit good thermal stability but much lower effieiency as compared to ordinary organic-inorganic hybrid perovskite.In order to further improve the power conversion efficiency of the all-inorganic cesium lead halide perovskite,this article addresses the problems of large interface carrier loss in all-inorganic perovskite solar cells and the energy level mismatch between the perovskite layer and the hole transport layer,research on the morphology control of the CsPbI₂Br perovskite film was carried out,and the internal relationship between the hole transport layer structure of the perovskite solar cell and the photovoltaic performance was explored.The main research results are as follows:(1)The effect of annealing temperature on the morphology and photoelectric properties of CsPbI₂Br perovskite film was clarified.When the temperature was in the range of 160? to 300?,the perovskite grain size was increased with increasing the annealing temperature.The perovskite films prepared under different annealing temperature conditions have high density and no pinholes.The perovskite film prepared at an annealing temperature of 250?has the highest crystallinity,the open circuit voltage of the device is 1.11 V,the short-circuit current density is 14.7 mA/cm²,the fill factor is 70.2%,and the power conversion efficiency of 11.1%is obtained.(2)Polytriarylamine(PTAA)is a commonly used hole transport material in perovskite solar cells,but the Highest Occupied Molecular Orbita(HOMO energy level)of this material has a large energy gap with the top of the valence band of CsPbI2Br perovskite,resulting in greater photovoltaic energy loss.By doping a small amount of Poly(N-vinylcarbazole)(PVK)with a deeper HOMO energy level into the PTAA hole transport layer,the energy gap between the hole transport layer and the perovskite layer was reduced,and the open circuit voltage of the solar cell was increased.By optimizing the amount of PVK doping in the PTAA:PVK hybrid film,the open circuit voltage was increased from 1.11 V for pure PTAA device to 1.19 V for PTAA:7.5%PVK device,and the PCE was increased from 11.1%to 13.6%.(3)The new organic polymer donor material D16 has shown good hole transport performance and a deep HOMO energy level(-5.48 eV).Therefore,CsPbI₂Br perovskite solar cell based on the hole transport layer of D16 was constructed.As a result,the short-circuit current density and open-circuit voltage(14.6 mA/cm² and 1.12V),and the FF and PCE(72.0%,and 11.8%)respectively,were achieved.Furthermore,a D16/PTAA double-layer hole transport layer structure was constructed,which has faster hole mobility than a typical PTAA transport layer and reduces carrier recombination loss.In addition,because D16 contains a thiophene group,it can effectively passivate the defect state of the surface of the perovskite film.Compared with conventional PTAA devices,the open-circuit voltage of D16/PTAA devices was increased from 1.09 V to 1.18 V,the fill factor was increased from 67.3%to 79.7%,and the power conversion efficiency was increased from 11.0%to 13.5%.