Comparison of different thin film absorbers used in eta-solar cells

Abstract 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 Cd x Hg 1− x Te (CMT). Alloy films have been incorporated as extremely thin absorbers in solar cells with the structure glass∣SnO 2 ∣microporous–TiO 2 ∣CMT∣Au. The decrease in the CMT bandgap is expected to reduce the conduction band offset at the interface to TiO 2 , which is 0.6 eV for the TiO 2 ∣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.