Thin Films Formed by Selenization of CuIn\u3csub\u3ex\u3c/sub\u3eB\u3csub\u3e1−x\u3c/sub\u3e Precursors in Se Vapor

Previous attempts in producing light absorbing materials with bandgaps near the 1.37 eV efficiency optimum have included the partial substitution of gallium or aluminum for indium in the CIS system. The most efficient of these solar cells to date have had absorber layers with bandgaps \u3c 1.2 eV. It is logical that an even smaller substitutional atom, boron, should lead to a wider bandgap with a smaller degree of atomic substitution. In this study, copper–indium–boron precursor films are sputtered onto molybdenum coated glass substrates and post-selenized. In the selenized films, although X-ray diffraction (XRD) measurements confirm that a CIS phase is present, Auger electron spectroscopy (AES) results indicate that boron is no longer homogeneously dispersed throughout the film as it was in the case of the unselenized precursor

A non-vacuum process for preparing nanocrystalline CuIn\u3csub\u3e1−x\u3c/sub\u3eGa\u3csub\u3ex\u3c/sub\u3eSe\u3csub\u3e2\u3c/sub\u3e materials involving an open-air solvothermal reaction

A non-vacuum, two-step process has been used to prepare a series of nanocrystalline CuIn1−xGaxSe2 (x = 0, 0.25, 0.5, 0.75, 1) materials. An open-air solvothermal preparation in triethylenetetramine solvent was followed by annealing at 500 °C in a nitrogen atmosphere for 20 min. All materials have mixed clustered plate, spherical particle, and nanorod morphologies with the smallest particle diameters ranging between 20 and 40 nm. Raman spectroscopy and X-ray diffraction (XRD) confirm that indium/gallium ratio control is possible over a wide range. The solvothermal reaction step yields a mixture of chalcopyrite and Cu2−xSe. This is converted to pure chalcopyrite product by annealing at 500 °C

REACTION PATHWAY INSIGHTS INTO THE SOLVOTHERMAL PREPARATION OF Culn\u3csub\u3e1- x\u3c/sub\u3eGa\u3csub\u3ex\u3c/sub\u3eSe\u3csub\u3e2\u3c/sub\u3e NANOCRYSTALLINE MATERIALS

Reaction pathway investigations of the solvothermal preparation of nanocrystalline Culn1- xGaxSe2 in triethylenetetramine reveal the early formation of a previously unreported Cu2-xSe(S) intermediate. Over 24 hours, this reacts with In and Se species to form CulnSe2(s). If Ga is present, the reaction proceeds over an additional 48 hours to form Culn1-xGaxSe2. Adding ammonium halide salts reduces the CulnSe2 formation time to as little as 30 minutes. It is proposed that in these cases, Cu2-xSe particle growth is limited via a competitive Cu-halide complex formation. The smaller Cu2-xSe particles may react and form CulnSe2 more rapidly. A reaction pathway scheme consistent with experimental results and previous literature reports is proposed