Structural investigations of copper incorporation into In‐Ga‐Se precursor layers for Cu(In,Ga)Se₂ thin films

Abstract

In the present work, the effect of the copper incorporation into the In‐Ga‐Se precursor layer during the stage 2 of the three stage growth process of Cu(InGa)Se2 thin films is investigated. Break‐off experiments at certain points during stage 2 were performed, corresponding to different [Cu]/([Cu]+[In]+[Ga]) ratios. The elemental distribution in the layers at the break‐off points was investigated by energy‐dispersive X‐ray spectroscopy on cross‐sections of the layers. Although stage 1 includes a sequential deposition of In‐Se and Ga‐Se layers, these layers appear completely mixed in the beginning of stage 2, i.e., compositional gradients are absent, after the deposition of copper and selenium at a substrate temperature of 525 °C during this stage. However, the deposition of copper and selenium at lower substrate temperatures and for short deposition durations, leading to [Cu]/([Cu]+[In]+[Ga]) ratios much smaller than 0.5, results in thin films in which the sequential order of the precursor layers remains clearly visible in the EDX profiles. Grazing incidence X‐ray diffraction measurements were carried out to investigate the formation of different phases, e.g., that of ordered vacancy compounds, during the incorporation of copper into the In‐Ga‐Se precursor layers. The influence of the copper incorporation on the Cu(In,Ga)Se2 lattice parameter is discussed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Cu deficiency in multi-stage co-evaporated Cu(In,Ga)Se2 for solar cells applications: Microstructure and Ga in-depth alloying

“…The highly homogeneous Ga distribution is thought to be related to a higher Ga mobility when more V Cu defects are present. This interpretation is consistent with our previous work [32], in which we also observed a homogeneous distribution of Ga when the process was interrupted at a point close to point A of Fig. 1.…”