Recombination in Cu(In,Ga)Se2 thin-film solar cells containing ordered vacancy compound phases

We investigated the transport and photovoltaic properties of Cu-deficient Cu(In1 − xGax)Se2 (CIGS) thin-film solar cells containing ordered vacancy compound (OVC) layers. Raman spectra clearly revealed that the CIGS thin films with lower Cu concentrations contained larger volumes of OVC layers. The temperature-dependent inverse ideality factor showed that the CIGS film containing more (less) OVC layers exhibited tunneling-mediated bulk (interface)-dominated recombination. The capacitance-voltage characteristics and admittance spectra showed that the CIGS cells containing more OVC layers had more uniform carrier concentration near the junction and less interfacial trap states compared with cells with less OVC layers. These results suggested that the Cu-deficiency and the resulting OVC layer formation reduced the interfacial defect density and suppressed the interface recombination processes of the CIGS solar cells.