Study On Dye-Sensitized TiO₂ Nanocrystalline Solar Cells

Dye-sensitized nanocrystalline TiO2 solar cell (NPC) is a new type of the photoelectrochemical solar cell. Because of its simple fabrication procedure, low cost, better stability and clean energy, NPC solar cell has arouse world researches and application prospect. The results are significant on the fields of semiconductor optoelectronics, nanoporous materials and solar cells. In this paper, the relations between the photoelectric properties and the assembly, structure, constitute of the cells were studied, and a NPC solar cell with higher incident photon-to-current conversion efficiency was obtained.(1) TiO2 film was obtained by uniformly applying Ti02 sol on the conductive glass plate, TiO2 sol was prepared by grinding the mixture of TiO2 powder (P- 25), water, dispersant acetylacetone and emulsification OP. The TiO2 film was heat treated at 400℃ for 30 min to remove some impurities and produce nanoporous. TiO2/dye electrode was fabricated by immersing the nanoporous TiO2 film into dye RuL2(SCN)2 solution for about 24h. The NPC cell was assembled by dropping an electrolyte solution into the space between the TiO2/dye electrode and the counter electrode and connecting an external circuit.(2) The influences of Ti02 films fabrication procedure conditions ?quantity of dispersant acetylacetone, quantity of emulsification OP, grinding time, heat treating temperature, time of keeping temperature and the thickness of TiO2 films on the photoelectric properties of NPC cells have been elaborately studied. The results show that there were better photoelectric properties under the condition of 0.15 mL of dispersant acetylacetone, 0.10 mL of emulsification OP, whetting for 60 min, heat treatment at 400℃ for 30 min and 11.4 um thickness of TiO2 film.(3) The photoelectric properties of NPC cells were improved with the cathode modified by catalyzing platinum, nickel and graphite. The short-circuit current increased from 0.91mA to 8.12mA, 5.23mA and 5.23mA respectively; the open-circuit voltage was changed from 478mV to 542mV, 468mV and 510mV respectively; the fill factorincreased from 0.09 to 0.47, 0.15 and 0.23 respectively; the incident photon-to-current conversion efficiency was raised from 7.59% to 48.32%, 41.19% and 18.92% respectively.(4) The influences of the exterior light on the photoelectric properties of NPC cells were studied. In some light intensity scope, the open-circuit voltage and short-circuit current increase with the increase of incident light intensity, but the fill factor decrease. In our experimental condition, the overall light-to-electric energy conversion efficiency of 0.95% was higher under the irradiation of 72.7mW/cm2 by simulated solar light. And the short-circuit current, the open-circuit voltage and the fill factor was 8.12mA, 542mV and 0.47 respectively. The maximal incident photon-to-current conversion efficiency was 48.32% at the wavelength 560nm.Under the irradiation of 43.31mW/cm2 sun light, The short-circuit current, the open-circuit voltage, the fill factor and the overall light-to-electric energy conversion efficiency for NPC solar cell was 10.45mA, 575mV, 0.36 and 1.55%, respectively.