Low temperature pulsed electron deposition and characterization of ZnS films for application in solar cells

Zinc Sulphide films were grown by pulsed electron deposition (PED) from room temperature to 350 degrees C to investigate the possibility of its application in solar cells, in particular as an alternative buffer layer deposited at low temperature. The films were characterized by X-ray diffraction, TEM, AFM, optical absorption and electrical measurements. ZnS films display crystalline structure and columnar growth at room temperature on amorphous substrate; the crystallization improves with the substrate temperature and is predominantly related to the cubic (111) orientation, while the thicker films show coexistence of hexagonal and cubic structures. All the samples have transparencies exceeding 70% in the range 400-1000 nm, energy band gap between 3.25 and 3.65 eV increasing with temperature and resistivity in the range of 10(4)-10(6) Omega cm. The optimization of the growth rate as a function of the growth parameters (substrate temperature and electron gun voltage) is also discussed. The reported results indicate that ZnS might be a suitable material for photovoltaic applications, specifically in process requiring low deposition temperature. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim