Recent developments in sensitized mesoporous heterojunction solar cells

The performance of solid-state dye-sensitized solar cells based on spiro-MeOTAD (2,2'7,7'-tetrakis(N, N-di-p-methoxyphenyl-amine)- 9,9'-spirobifluorene was considerably improved by decreasing charge recombination across the interface of the heterojunction. This was achieved by blending the hole conductor matrix with a combination of 4-tert-butylpyridine (tBP) and Li[CF₃SO₂]₂N. Open circuit voltages (U_OC) over 900mV and short circuit currents (I_SC) up to 5.1 mA were obtained, yielding an overall efficiency of 2.56% at AM1.5 illumination. Further improvement of the device performance was observed when conducting stripes of silver were deposited onto the devices as charge collector. The beneficial effect however could be assigned to the contamination of the dye-sensitized TiO₂ film with silver during the dyeing process.