The TiO_2 nanoporous film photoelectrode,as a crucial component of dye-sensitizedsolar cells,has been investigated.The photovoltaic properties and the dark current were studiedby two surface modification methods.One was to apply a compact layer between the conductiveglass substrate and nanoporous TiO_2 film.Another was to produce TiO_2 nanoparticles amongthe microstructure by TICl_4 treatment.A suitable concentration and number of times for TiCl_4treatment were found in our experiment.The dark current is suppressed by surface modifications,leading to a significant improvement in the solar cells performance.An excessive concentrationof TICl_4 will produce more surface states and introduce a larger dark current reversely.The dyeis also regarded as a source of charge recombination in dark to some extent,due to an amountof surface protonations introduced by the interfacial link in the conductive glass substrate/dyeinterface and dye/TiO_2 interface.
