Improved performance of dye-sensitized solar cells with novel conjugated organic dye using aluminum oxide-coated nanoporous titanium oxide films

This work introduces the TiO2/dye/electrolyte interface in the recombination and offers an interface treatment method using solution process for dye-sensitized solar cells (DSSCs). Solution-processed ultra-thin metal oxides introduce to treat the surface of mesoporous TiO2 to reduce the defect density and improve the electronic quality. Among the metal oxides, an Al2O3 barrier is incorporated into DSSCs as a carrier-recombination blocking layer. In all instances, the short-circuit current density increase and the dark current is suppressed after Al2O3 deposition. The impact of the Al2O3 barriers is also studied in devices employing different dyes. To compare the behavior of metal-free organic dyes and Ru dyes when Al2O3 barrier layers are involved, the charge transfer between the dye and TiO2 electrodes, associated with interfacial electron injection, is investigated by Raman spectroscopy. The metal-free organic dye had a high molar extinction coefficient and better adsorption properties compare to Ru dye, which resulted in higher charge-collection efficiency. To verify the strategy, the DSSCs photovoltaic performances containing these dyes are compared using their current-voltage curves. Electrochemical impedance spectroscopy (EIS), Intensity Modulated Photocurrent Spectroscopy (IMPS), and Intensity Modulated photoVoltage Spectroscopy (IMVS) were used to further investigate the kinetics process of the TiO2 film electrodes.