Charge interaction and interfacial electronic structures in a solid-state dye-sensitized solar cell

Fully solid-state dye-sensitized solar cell (DSSC) has attracted much recent attention. While the origins of the lower performance in DSSC using solid electrolyte are not fully understood, there is so far no report on their interfacial electronic structures. Here, we report the charge exchange and interfacial energetics in a standard solid-state DSSC with a structure of FTO/TiO₂/cis-disothiocyanato-bis(2,2′-bipyridyl-4,4′- dicarboxylato) ruthenium(II) bis-(tetrabutylammonium) (N179 dye)/2,2,7,7- tetrakis-(N,N-di-pmethoxyphenyl-amine) 9,9-spirobifluorene (spiro-OMeTAD). While the electron-extracting barrier at TiO₂/N719 interface is negligibly small (0.19 eV); the abrupt vacuum levels (VLs) offsets at N719/spiro-OMeTAD interfaces results in large hole-extracting barrier of 0.43 eV. Our results suggest an electronic mismatch in charge collection using spiro-OMeTAD as the hole-conducting material. © 2013 Elsevier B.V.