Effects of HCl and Methanol in the Precursor on Physical Properties of Spray-Deposited Nanostructured CuO Thin Films for Solar Applications.

The influence of the presence of HCl and methanol in the precursor on CuO absorber layers deposited by spray pyrolysis has been investigated. The films were deposited on glass substrate at fixed substrate temperature of 450°C using 0.05 molar CuCl·2HO in deionized water containing a specific amount of HCl and methanol. The structural, morphological, electrical, and optical properties of the resulting thin films were studied to evaluate their suitability for solar applications. Presence of HCl increased the concentration of Cu ions in the precursor, leading to a rise in the Cu concentration in the resulting film, which improved the crystallinity with increased mean grain size, surface roughness, and carrier mobility at the cost of decreased carrier concentration. However, film deposited with excess HCl suffered from corrosion and huge cracks, making it unfavorable for solar applications. On the other hand, although presence of methanol improved the crystallinity of the resulting film, the surface was smooth due to lower deposition rate. Kubelka-Munk theory was used to estimate the optical bandgap of the deposited thin films, revealing values fairly close to optimum for solar cell applications. [ABSTRACT FROM AUTHOR]