Alloying with mercury (Hg) has been used in electrodeposition as a means to reduce the bandgap of CdTe absorber films from 1.5 eV for CdTe to 1.07 eV for CdxHg1-xTe (CMT). Alloy films have been incorporated as extremely thin absorbers in solar cells with the structure glass\SnO2\microporous-TiO2\CMT\Au. The decrease in the CMT bandgap is expected to reduce the conduction band offset at the interface to TiO2, which is 0.6 eV for the TiO2\CdTe interface. This high band offset was believed to be responsible for the low fill-factor observed in the J-V characteristics of the former interface. Lowering the band offset is expected to lead to higher fill-factor values. Our results show that using a CMT as absorber gives place to both higher quantum efficiencies and a spectral response spectrum extended towards longer wavelengths, but not to a fill-factor enhancement. (C) 2003 Elsevier Science B.V. All rights reserved.