Fabrication And Characterization Of Conventional And Inverted Polymer Solar Cells

Polymer solar cells (PSCs) belong to the third generation of solar cells,which have been one of the hot research fields facing the increasingly seriousenergy problems in the world today for human society. Because of itsappropriate energy level and excellent optical properties, titanium dioxide hasbeen widely used in inverted organic solar cells. Electrochemical impedancespectroscopy analysis which was used widely in dye-sensitized solar cellscould be helpful for a better understand of interface states in organic solarcells. In this paper, convetional and inverted polymer solar cells werefabricated exposed to the air and optimized, and electrochemical impedanceanalysis was used to characterize the devices trying to get a betteruncerstanding of PSC interface states.Firstly, TiO2inorganic buffer layers, such as TiO2thin film, TiO2nanotube film and TiO2nanorod array film, were fabricated and studied to getfilms of high quality and adjustable thickness. Scanning electron microscopy(SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD),high-resolution transmission electron microscopy (HR-TEM), selected areaelectron diffraction (SAED) and other characterization methods were appliedto characterize the samples. Finally uniform TiO2film without cracks wasfabricated, as well as morphology adjustable TiO2nanorod array films.Convetional polymer solar cells were fabricated by spin-coating of P3HTand PCBM, as active layer material, soluted in chlorobenzene. UV-visiblespectrophotometer (Uv-vis), photoelectric conversion efficiency etc. wereapplied to find how the spin rates and the concentration of the active layersolution affect the active layer thickness and finally the cell performance.Zinc acetate introdeced as protective layer for the active layer, and thethermal evaporation conditions, were both proved to have effects on the cellperformance. Finally an optimized PCE of2.35%for the convetional polymer solar cells was achieved.With TiO2film or TiO2nanorod array film as electron transport layer,graphite oxide as hole transport layer, inverted polymer solar cells werefabricated and optimized, with0.857%and0.535%as the best PCE achieved,respectively.Electrochemical impedance spectroscopy was applied to study how thefabrication parameters affect the cell performance, giving a better understandof the carrier dynamic behaviors in the cells, providing a clearer direction forthe optimization of polymer solar cells.