Light scattering enhanced photoanodes for dye-sensitized solar cells prepared by carbon spheres/TiO_2 nanoparticle composites

摘要

Incorporating scattering centers in the nanocrystalline photoanode or additional scattering layers on the nanocrystalline photoanode is an effective way to enhance the light harvest efficiency (LHE) of the photoanode and the performance of dye-sensitized solar cells (DSSCs). In this work, mesoporous photoanodes were fabricated based on the composites of anatase TiO_2 nanoparticles and carbon spheres. The holes were left after calcination thus serving as the light scattering centers in the photoanode. The size and the amounts of the holes were adjusted by changing the size (250, 500 and 700 nm) and concentration (5, 10, 15 and 20 wt% of the TiO_2 nanocrystallines) of the carbon spheres in the slurry. The light scattering ability and the dye adsorption of the photoanodes with holes of varied size and contents were investigated. The holes left by calcinating the carbon spheres increased the light scattering of the photoanode. However, the increased light scattering ability offset the dye adsorption ability of the photoanode by high amounts of carbon spheres modification. The performances of the DSSCs are investigated under the simulated sunlight and the incident light (400-780 nm). The DSSC with photoanode made from the slurry with 500 nm and 15 wt% carbon spheres exhibited the opitimized performance (Jsc = 14.8 mA cm-2, Voc = 0.657 V, FF = 0.703 and η = 7.2%), much better than the DSSCs with photoanode made by the pure TiO_2 nanocrystalline (Jsc = 11.7 mA cm~(-2), Voc = 0.645V, FF = 0.699 and η = 5.55%) and other photoanodes, indicating it best balanced the controversy of the enhanced light scattering ability and the decreased dye adsorption. The incident-photo-to-electric conversion efficiency test indicated the highest LHE of the 500 nm and 15 wt% carbon spheres modified photoanode.