TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Photovoltaic Cell Structure: The rough surface has a roughness of 0.01-100 mu m. The rough p-n junction has a roughness of 0.01-100 mu m. The substrate is a glass substrate, a polyimide flexible board, a metal plate or a metal foil of stainless steel, molybdenum, copper, titanium, or aluminum. The metal layer comprises molybdenum. The n-type semiconductor layer comprises cadmium sulfate, zinc sulfate or indium sulfate. The photovoltaic cell structure further comprises a carrier barrier layer between the n-type semiconductor layer and the transparent conductive layer. The transparent conductive layer comprises indium tin oxide, indium zinc oxide, aluminum zinc oxide, gallium zinc oxide, aluminum gallium zinc oxide, cadmium tin oxide, zinc oxide, or zirconium dioxide. Preferred Method: The substrate is a glass substrate, and roughing the substrate comprises etching and sand blasting. Roughing the substrate comprises sand blasting followed by etching. Etching uses hydrofluoric acid. Alternatively, substrate is a metal substrate, and roughing the substrate comprises etching or mechanical embossing. Roughing the substrate comprises: (i) forming a first metal film on the substrate; (ii) roughing the first metal film by etching; and (iii) forming a second metal film on the first metal film. The metal layer is formed by sputtering. The p-type semiconductor layer is formed by co-evaporation from elemental sources, selenization of metallic precursor layer, evaporation from compound source, chemical vapor deposition, close-spaced vapor transport, spray pyrolysis, electrodeposition, low temperature liquid phase method for precursor deposition, or chalcogenization of particulate precursor layer. The method further comprises forming a carrier barrier layer before forming the transparent conductive layer on the n-type semiconductor layer; the carrier barrier layer is formed between the n-type semiconductor layer and the transparent conductive layer.