Charge Transfer Layer Modification In The Mesoscopic Structure Perovskite Solar Cells

With the existence of energy crisis,clean,renewable solar energy is developing rapidly.In the use of solar energy,solar cells are considered as one of the most effective conversion methods.Perovskite solar cells(PSC)has become a rising star in the field of photovoltaics due to their low cost and high photoelectric conversion efficiency.Mesoporous PSCs usually use metal oxide nanoparticles as the mesoporous layer to achieve the role of transporting electrons and supporting the perovskite layer,thereby obtaining more desirable photoelectric conversion efficiency.TiO2 nanospheres are excellent mesoporous materials on account of their excellent electron transport properties and high specific surface area.Studies of this dissertation concentrate on the development of mesoporous PSCs based on TiO2 nanospheres.By adjusting the types and ratios of solvents and additives,TiO2 nanospheres with three different mesoporous structures are prepared by one-step hydrothermal method and assembled into PSC devices.Through the test of its photoelectric properties,the TiO2 mesoporous materials suitable for PSC are finally obtained,and a design idea is provided for the preparation of high efficient PSC mesoporous materials.Firstly,acetonitrile,isopropanol and acetylacetone are used as the solvent system,and n-tetrabutyl titanate was selected as the titanium source.By changing the amount of additives,TiO2 cookie spheres with controllable size and structure were prepared.TiO2 cookie ball with a uniform diameter(300 nm)and a good monodispersity is prepared into a slurry,mixed with a commercial P25 slurry in different proportions,and then a corresponding mp-TiO2 is prepared on a FTO substrate with a dense layer.On this basis,the PSC device is assembled and tested for optoelectronic performance using methylamine lead iodine(MAPbI3,MA =CH3NH3)as the light-absorbing layer material of the PSC cell.The results show that compared with the P25-based PSC,the TiO2 film prepared by mixing the TiO2 cookie ball with the P25 slurry is favorable for the infiltration of MAPbI3,and when the P25 and TiO2 cookie balls are mixed in the ratio of 1:1,they can improve the light absorption capacity and short-circuit current density of the PSC significantly,and will finally get the photoelectric conversion efficiency of 14.46%,which is better than the efficiency based on the commercial P25 PSC.Secondly,using isopropanol and acetylacetone as solvent systems and changing the amount of additives at the same time,then we get hollow TiO2 nanospheres with controllable size.Hollow TiO2 nanospheres with a uniform diameter distribution(500 nm)and good monodispersity are prepared into a slurry and mixed with P25 slurry in different proportions to prepare corresponding PSC electron transport layers and assembled into PSC devices respectively.Performance Testing.The results show that the TiO2 mesoporous layer prepared by mixing 500 nm hollow spheres with P25 is conducive to the infiltration of MAPbI3.On account of multiple reflections of visible light by the hollow TiO2 nanospheres,the light absorption capacity of the assembled PSC is greatly enhanced,thereby effectively increasing the short-circuit current density of the battery.When hollow TiO2 nanospheres and P25 are mixed in the ratio of 1:1,we will get the PSC with a photoelectric conversion efficiency of 17.64%.The electrochemical kinetics of the PSC interface is analyzed by electrochemical impedance spectroscopy.The results show that when the TiO2 mesoporous layer is mixture of P25 and TiO2 cookie spheres in the ratio of 1:1,the transmission resistance of the PSC is significantly reduced.Finally,on the basis of the isopropanol and acetylacetone solvent system,by changing the ratio of the two solvents,we will get elliptic ball TiO2 nano-particles with a short axis of about 500 nm.The slurry is prepared into a slurry and mixed with the P25 slurry in a certain ratio to prepare a PSC electron transport layer,and a PSC device is assembled to perform performance testing.The results show that after the elliptic ball TiO2 particles are incorporated into the electron transport layer,the thickness of the cap layer increases,and the grain boundary of the perovskite layer decreases,so that the electron-hole recombination probability decreases and the open circuit voltage increases.In this dissertation,acetonitrile,isopropanol and acetylacetone are used as the solvent system.By adjusting the solvent ratio and controlling the amount of additives,controlled size TiO2 nanospheres,hollow TiO2 nanospheres and elliptic ball TiO2 nanoparticles were prepared.The three TiO2 nanomaterials are mixed with commercial P25 in proportion to prepare an electron transport layer and assembled into a corresponding PSC cell.After performance tests,it is found that the high specific surface area and special dielectric properties of the prepared TiO2 nanomaterials by observing the structure can effectively improve the light utilization rate of the perovskite layer,thereby obtaining a PSC device with a higher photoelectric conversion efficiency.