Ex-situ and in-situ selenization of copper-indium and copper-boron thin films

It has recently been established that the ideal bandgap for terrestrial photovoltaics is 1.37 eV and the bandgap for CuInSe2 is only around 1.04 eV. Thus, a larger bandgap is needed. However, neither the substitution of Ga nor of Al has made a high efficiency solar cell absorber with a band gap of 1.37 eV possible. B, an even smaller atom, should require less atomic substitution than either Ga or Al to achieve a wider bandgap. In order to fabricate a thin film of CuInxB1-xSe2 (CIBS), Cu, In and B were deposited from a variety of sputtering targets which were pure Cu, In, and B; a Cu.45In.55; and a Cu3B2 target. Films were deposited simultaneously and sequentially. After deposition these films were post selenized in another vacuum chamber. Analysis of these films was accomplished using Raman spectroscopy, X-ray diffraction (XRD), and Auger electron spectroscopy (AES). With the difficulties encountered, materials were also deposited in a selenium atmosphere.