Study On The Effect Of Dye Adsorption On Properties Of Dye-sensitized Solar Cells

Dye-sensitized solar cell （DSC） is a new photoelectric conversion technology thatreported by Swiss Gr tzel group in1991. As the most developmentally-prospectivephotoelectric conversion technology at present, DSC is more economical andenvironmentally-friendly than conventional solid semiconductor solar cells, and DSCcan obtain effective photoelectric conversion efficiency as well. However, photoelectricconversion efficiency of DSC is now much lower than its theoretical efficiency.Therefore, further in-depth study of DSC is still needed.The interfacial charge recombination effect is the dominant factor that impeded thephotoelectric conversion efficiency of DSC. The main process of interfacial chargerecombination takes place in the interface of TiO₂/dye/electrolyte where injectedelectrons （photogenerated electrons） are captured by triiodide （I₃^-） in the electrolyte. Inthe TiO₂/dye/electrolyte interface, the high concentration of dye molecules adsorbed onsurface of TiO₂may cause high local concentration of I₃^-, which finally increase theprobability of interfacial charge recombination effect. The open circuit voltage, shortcircuit current and fill factor of DSC would be declined because of interfacial chargerecombination effect so that the power conversion efficiency would be hindered.Therefore, this paper aims to explore the impact of dye adsoption concentration of DSCon its interfacial charge recombination effect and photoelectric conversion performanceby altering the dye adsorption concentration on the TiO₂surface.DSC with different dye adsorption concentration can be obtained througth alteringthe dye solution concentration for soaking TiO₂film, dye solution soaking time of TiO₂film, and loading similar among of dye on TiO₂film with different thickness. Twoconclutions could be drawn from EIS anlysis of interfacial electron transport in DSCwith different dye adsorption concentration. The lower of the dye adsorptionconcentration of TiO₂film, the higher the electron transport resistance inTiO₂/dye/electrolyte interface is. This means the back transfer of electrons on theinterface is difficult. The lower of the dye adsorption concentration of TiO₂film, thelarger the diffusion coefficient is. These two results both illustrate that the interfacialcharge recombination effect of DSC decrease when the dye adsorption concentration isrelatively low.Study of photoelectric conversion performance of DSC assembled by TiO₂film with different dye adsorption concentration indicated that the open circuit voltage, shortcircuit current and power conversion efficiency increased with the increase of dyeadsorption concentration. Low dye adsorption concentration was not beneficial toimprove the open circuit voltage, short circuit current and power conversion efficiencyof DSC. However, fill factor, the measure of interfacial charge recombination, decreasedwith the increase of dye adsorption concentration. High fill factor appeared in low dyeadsorption concentration situation, which indicated low dye adsorption concentration ofDSC could weaken the interfacial charge recombination effect.