Chemical sintering of graded TiO2 film at low-temperature for flexible dye-sensitized solar cells

A mesoporous nanocrystalline graded TiO2 film was prepared on either a transparent conductive glass (ITO/glass) or a transparent conductive polymer (ITO/PEN, PEN = poly(ethylene naphthalene-2,6-dicarboxylate) through a doctor-blade method and then treated by chemical sintering at 150 °C. The graded film, which has a large specific surface area, high porosity, and proper strength, was composed of particles with different sizes and appropriate ratios. The effects of the smallest particles for binding and the largest particles for light scattering were studied. High light-to-energy conversion efficiencies of 4.10% and 3.05% were obtained within the dye-sensitized solar cells (DSSCs) fabricated by using the graded films on ITO/glass and ITO/PEN, respectively. The results show that the graded structure has promising applications in DSSCs.