Contacts to a solar cell with extremely thin CdTe absorber

Abstract The concept for a solar cell with extremely thin absorber (eta-cell) comprises a porous TiO 2 substrate covered by a CdTe film with a local thickness of 150–250 nm. At the present stage of development this type of cell exhibits a photovoltage between 600 and 700 mV and a photocurrent of 5–9 mA/cm 2 under AM1.5 illumination, indicating the feasibility of the concept. The fill factor is, however, only in the range of 20%, due to a strong voltage-dependence of the photocurrent. This paper discusses the influence of the front and back contacts on the limited cell performance and shows that the insertion of a buffer layer at the front contact gives an improved fill-factor.