The Study On Alkali Metal Doped (CMA)₂MA_n-1Pb_nI_3n+1 2D Thin Films And Solar Cells

Organic-inorganic hybrid perovskite solar cells have the advantages of low cost and high efficiency,so they have a wide range of application prospects.Its efficiency has improved from 3.8%to 25.5%in just 10 years.However,the humidity and thermal stability of conventional 3D perovskite solar cells are poor,and the problem of stability is the bottleneck of limiting the large-scale application of perovskite solar cells.In recent years,two-dimensional perovskite has attracted widespread attention due to its high humidity stability.However,two-dimensional perovskite solar cells have low photoelectric conversion efficiency due to poor carrier transport.Therefore,on the premise of maintaining good stability,improving the conversion efficiency of two-dimensional perovskite solar cells is a key problem in its current research.In view of the above two-dimensional perovskite material problems,By preparing(CMA)₂MA_n-1Pb_nI_3n+12D perovskite film and doping of alkali metal,Expect to be efficient and stable 2D-RP perovskite solar cells.The main research contents are as follows:(1)The properties of (CMA)₂MA_n-1Pb_nI_3n+1two-dimensional perovskite films and devices based on CMA with different values of n are studied.Through the study of n=4,6,7,9 two-dimensional perovskite,it is found that the two-dimensional perovskite film based on CMA is a heterogeneous mixture and has an inverted trapezoidal quantum well distribution,That is,components with small n values(high stability)are mainly distributed on the surface,and components with large n values(good charge transport)are distributed on the bottom.Due to the protection of the small n-value film on the surface,this structure can simultaneously have high stability and good charge transport characteristics.As the value of n increases,the intensity of the vertical-oriented diffraction peaks in XRD continues to increase.The vertically-oriented crystals in the films with n=7 and n=9 dominate,and they have good charge transport characteristics.The photovoltaic performance of solar cells based on n=7 and 9 is better than the devices of n=4 and 6,and the highest efficiency of the devices of n=7 and 9 are both greater than 10%.(2)The film properties and device performance of the alkali metal(CsI/KI)doped(CMA)₂MA_n-1Pb_nI_3n+1(n=7,9)two-dimensional perovskite were studied;Through the study of two-dimensional perovskite films and batteries with doping concentrations of 0%,3%,5%,10%,and 15%,it is found that:1)n=7(CMA)₂MA₆Pb₇I₂₂perovskite films prepared with different CsI doping concentrations.CsI can significantly improve the thermal stability of the perovskite film,improve the surface of the film,increase the grain size and reduce defects,thereby improving the quality of the film.Finally,the efficiency of the cell prepared by using the thin film Cs₁₀-2D with a doping concentration of 10%reached 12.57%,Which is nearly 26%higher than the undoped sample.2)The effect of different CsI doping concentration on the(CMA)₂MA₈Pb₉I₂₈film and battery with n=9 is similar to that of n=7.Due to the high content of vertically-oriented crystals in the n=9 film,it has better carrier transport properties,and its efficiency reaches 14.57%.3)The effect of different KI doping concentration on(CMA)₂MA₈Pb₉I₂₈film and battery.K⁺ion radius is much smaller than Cs⁺,incorporation of interstitial atoms into the perovskite film,Incorporating interstitial atoms into the perovskite film can passivate defects more effectively,The battery prepared by KI doping has an open circuit voltage as high as 1.21V;And K⁺ions significantly improve the transport characteristics of the film,so that the fill factor of the battery is increased to 0.81.The highest efficiency reached 22.28%.The performance of the two-dimensional perovskite battery prepared by KI doping is significantly better than that of the CsI doped device.