Research On Perovskite Layer Optimization And Interface Engineering On Carbon-based All-inorganic Perovskite Solar Cells

The development and utilization of solar energy have been always the frontier research direction of energy science.In recent years,to overcome the development bottleneck of silicon solar cells and thin-film solar cells,the third generation photovoltaic cells-perovskite solar cells(PSCs)have been surprised in the entire photovoltaic field due to their higher efficiency,larger commercial value,lower costs simpler processes and the fastest development.Until now,the highest PCE of PSCs certified by the National Renewable Energy Laboratory(NREL)has been reached 25.5%,which further enhance peoples'confidence in promoting the industrialization of perovskite solar cells.Although traditional organic-inorganic hybrid perovskite solar cells have been achieved the remarkable photovoltaic efficiency,their long-term stability are inevitably restricted because the organic components(such as methylamino MA+and methyl FA+)are easily thermal decompositionAll-inorganic cesium lead halide system CsPbI3-xBrx(x=0,1,2 and 3),which is formed by substituting the inorganic Cs cation for volatile organic groups,is an effective candidate for improving the intrinsic environmental tolerance of perovskites.Especially,carbon-based PSCs produced by the low cost gand simple film preparation conditions become the hotspots of many researchers and provide a promising commerical prospect.In this work,the carbon is used as the back electrode.In order to obtain the high efficient and stable all-inorganic PSCs,the serious carrier recombination caused by surface defects,and poor crystalline quality of all-inorganic perovskite films are improved by as the interface modification of the mesoporous scaffold layer,the component engineering of precursor solution and the aged mechanisms of perovskite solutions.The main research results are shown as follows(1)All inorganic CsPbBr3 mesoporous perovskite solar cells with interface modificationIn order to broaden the light response range of the perovskite absorption layer,a series of core/shell-structured upconversion nanoparticles,NaNbO3:Yb3+/Tm3+@SiO2,was successfully synthesized by solvothermal method,and furtherly integrated into the TiO2 mesoporous layer in CsPbBr3 PSCs.It is found that the NaNbO3:Yb3+/Tm3+@SiO2 not only acted as the scattering centers to increase the reflection of sunlight,but also suppressed electron-hole recombination at the TiO2/CsPbBr3 interface.In addition,the incorporating NaNbO3:Yb3+/Tm3+SiO2 in mesoporous layer was beneficial to improve the purity of CsPbBr3 phase and the crystallinity of perovskite film.Based on this strategy,the optimized champion CsPbBr3 PSCs with addition of NaNbO3:Yb3+/Tm3+@SiO2(6 wt%)exhibited the best open-voltage(Voc)as high as 1.52 V and a PCE of 9.20%.Compared with the unimproved CsPbBr3 solar cell,the increased PCE of 9.20%from 6.90%yielded an improvement by 33.3%,providing a new opportunity for reducing the Voc losses and raising the photocurrent in the mesoporous structure of all-inorganic PSCs devices.(2)Component engineering of acetate-DMA system assisted preparation of all-inorganic perovskite solar cell CsPbl3-xBrx(x?1).Under environmental conditions,the all-inorganic perovskite film of DMA system displayed the loose rough morphology and unacceptable pinholes due to the erosion of water and oxygen.In this work,lead acetate PbAc2was used to partially replace the lead source DMAPbI3,which could regulate the composition of the perovskite precursor solution.The experimental results proved that Ac-weakened the interaction between the intermediate state DMA-and PbI3-,simultaneously accelerated the sublimation of DMA and effectively controlled the crystallization process of the perovskite films.After the high temperature annealing(180?).the champion CsPbl3-xBrx perovskite solar cells,exhibiting the lower trap density,longer carrier life and faster charge transfer,achieved 13.10%photoelectric conversion efficiency and the good stability.In addition,the heavy doping of Ac-reduced significantly the annealing temperature,and the residual Ac-could passivated the film defects at the grain boundaries.The PSCs with the high efficiency of 10.72%shown almost no efficiency decay placed for one month under low humidity conditions and the low temperature annealing of 120?.(3)Research on aging management of CsPbI3 perovskite based on DMA systemFor the conventional solution method for PSCs,it is necessary to consider the stability of raw materials in the solutions since the PSCs were produced by dissolving the various raw materials into a polar solvent undergoing stirring and heating for a certain period.The effect of aging management on the the organic component DMA in the preparation of all-inorganic CsPbI3 perovskite were studied.The solutions deprotonation and passivation through tracking the composition characterization of the aging process is clear demonstrated.The crystallinity and morphology of the CsPbI3 perovskite film is improved,and the trap density is suppressed after I3-was formed.In addition,the Fermi level of the CsPbI3 is changed by the formed I3-to show heavy n-type doping.Based on the solar cell using the aged solution,the Voc was amazingly from 0.89 V increased to 0.99 V,with the photoelectric conversion efficiency improved to 12.06%coupled with favored storage and operational stability.