Sb2Se3 Thin Films for Doping the Absorber in CdTe Solar Cells

Nowadays, the primary efforts in CdTe solar cell research aim to find an alternative to copper doping among the group V elements. In fact, Cu has limited solubility in the CdTe grains, which prevents the achievement of higher open circuit voltages (Voc), and it is also a fast diffuser, considered the main factor of device degradation. Achieving effective doping with an alternative element could lead to improved Voc and, hence, cell efficiency, as well as increased stability. This study presents a novel method to dope CdSeTe/CdTe devices by depositing a thin Sb2Se3 layer on top of the absorber. Sb is then driven inside the CdTe matrix by subsequent CdCl2 treatment; the choice of Sb2Se3 prevents the introduction of additional impurities. This method proves to be effective because Sb-doped cells achieve efficiencies close to Cu-doped ones. On the other hand, in accelerated stress tests without encapsulation, Sb-containing devices are much more stable than Cu-doped ones, showing the same noteworthy stability as undoped devices.