Comparison of Mo and ITO back contacts in CIGSe solar cells: Vanishing of the main capacitance step

Admittance measurements of Cu (In, Ga)Se2 (CIGSe) solar cells typically show at least one capacitance step, the so-called N1 signal. Its origin is still under debate, even though signal present in almost all CIGSe cells. In this work, with different absorber layer thicknesses have been prepared on Mo and indium tin oxide (ITO)-based back contacts. The samples were analyzed by temperature-dependent current–voltage (JV) admittance measurements. No was found for ITO-based samples. also absent Mo-based an ultrathin layer, unless a forward bias voltage applied. observations can be consistently explained contact barrier, which only explanation further supported measured JV curves theoretical simulations. results give strong indication that N1-signal due to barrier. While barrier not necessarily detrimental regular cells, it may issue absorbers, where punch-through effect occur.