Study On The Fabrication And Photovoltaic Properties Of Carbon Based Novel Perovskite Solar Cells

Solar cells are devices that utilize the photoelectric effect of semiconductor materials to transform solar energy to electricity.Solar cells can make it convenient for some remote but well-lighted regions such as deserts and mountain districts to use electricity.Organic-inorganic hybrid perovskite ABX3?A = CH3NH3+,?MA?CH?NH2?2+?FA?,Cs+,B = Pb2+,Sn2+,X = Cl-,Br-,I-?used as sunlight absorption materials have great photovoltaic properties like suitable energy gap?1.5-2.3 e V?,larger absorptivity and charge mobility etc.,and have attracted many researchers' attention.Tunable band gap perovskite solar cells can be made of different adjusted components of perovkite materials.The flexible perovskite solar cells can be used to make wearable electronics.Compared to high temperature treated and high energy consumed silicon solar cells,perovskite solar cells are superior in low cost,relatively simple fabrication process such as spin-coated and screen-printed.Furthermore,the photovoltaic conversion efficiency of perovskite solar cells are increasing dramatically from 3.8% to 23.7% in few past years,its increment speed is more lager than other solar cells.In this thesis,the mixed mesoporous layer was used to replace the two-layer mesoporous structure and the single-layer TiO₂ mesoporous structure,so as to increase the grain size of the layered perovskite film and improve the efficiency of the layered perovskite solar cell.Then,the interface contact between the surface rutilized anatase TiO₂ and the perovskite grains was used to analyze the different performances of TiO₂ with pure anatase in layered and filled perovskite.Finally,the filled perovskite solar cell was prepared and its carbon electrode was improved.The following research results were obtained:?1?A mixed paste of TiO₂ and ZrO₂ was prepared.A large pore size in mixed mesoporous film was prepared by using the 50 nm of ZrO₂.The gap of the porous film provide enough space for the growth of the perovskite grains,and thus the perovskite grains have transformed from strip grains into bulk grains.The impacts of four different mesoporous films ZrO₂,TiO₂,mixed mesopores and TiO₂/ZrO₂ on the performance of perovskite solar cells were compared.The results show that the perovskite solar cell prepared by the mixed mesoporous film has the best performance,the short circuit current can reach to 21.89 m A/cm2,the open circuit voltage is 0.95 V,the filling factor is 60.90%,and the photoelectric conversion efficiency reach to 12.62%.?2?Surface anatase TiO₂ nano crystals were prepared by hydrothermal method and compared with pure anatase phase TiO₂.When the anatase phase of TiO₂ mesoporous film is used as a mesoporous layer,the oxygen vacancies on the surface will affect the stability of the perovskite layer and the devices.After the surface of the anatase phase TiO₂ is rutilized,the exposed?001?facet has a higher surface energy and improved interaction between perovskite/TiO₂.The rutile phase has a higher conduction band energy level,which is more compatible with the perovskite conduction band energy level and reduces interfacial recombination.The rutilized surface also promotes charge transfer between the grains.The prepared filled perovskite solar cells exhibited higher photovoltaic conversion efficiency,while in the spin-coated perovskite solar cells,the surface rutilized anatase TiO₂ failed to exhibit better photovoltaic conversion efficiency.This derives from the different transport rate of carriers in two kinds of structures.?3?Triple-layered mesoporous hole-conductor-free carbon-based perovskite solar cells were prepared by adding carbon fiber to carbon electrode.Carbon fiber is good conductive nanomaterial.It has large aspect ratio and specific surface area.It is an ideal conductive agent,which can build bridge between graphite and improve the bond strength between active materials.In the filled perovskite structure,the fibers in the carbon electrode are staggered vertically and horizontally to provide a permeation channel for the perovskite solution,and improve the filling fraction of the perovskite solution in the mesopores,and an isolated perovskite layer formed at the interface.Interfacial contact improved between the perovskite crystals and carbon electrode,thus accelerating the transport of carriers and improving the photoelectric performance of the devices.