Investigation of Mg(O,OH) Films Prepared by Chemical Bath Deposition as Buffer Layers for Cu(In,Ga)Se2 Solar Cells

The buffer layers of magnesium compound semiconductor were deposited on the soda-lime glass substrates by the chemical bath deposition (CBD) process. Prepared with ammonia (NH4OH) and magnesium sources of MgCl2 or Mg(CH3COO)(2) at the bath temperature of 50 degrees C, the as-deposited films containing magnesium oxide and magnesium hydroxide were verified by X-ray photoelectron spectroscopy (XPS) analysis of binding energies of magnesium and oxygen. Thus, the films described in this study refer to a magnesium compound better characterized as Mg(O,OH). The surface morphologies of Mg(O,OH) films were assessed by field emission scanning electron microscope (FESEM). The smooth surface morphologies of Mg(O,OH) films with a conformal coverage on the glass substrates were achieved by optimizing the ammonia and magnesium salt concentrations in the deposition bath. The Mg(O,OH) films had a preferred (002) orientation corresponding to a hexagonal crystal structure. The band-gap energy of as-deposited Mg(O,OH) films was determined from the optical absorption data, revealing the optical band-gap energy of around 5.17 eV. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3609047] All rights reserved.