TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Substrate: The substrate on which the zinc oxide layer is formed is a substrate having a high surface energy, preferably 40 mN/m. The substrate is glass, polyethylene terephthalate, or indium-tin oxide layer on a support. The electrode layer comprises indium-tin oxide. Preferred Conditions: The dry film is heated at 140 degrees C for at least 5 minutes in the presence of humidity. The hole transport layer is formed by coating the active layer with a solution of hole conducting compound in water and/or alcohol or mixture of alcohols to form a film, and drying the film. The active layer is wetted with an alcohol prior to coating. The alcohol used to wet the active layer and the alcohol used in the coating solution is isopropanol. The electrode is a metal electrode. The electrode is formed by coating an ink comprising metal flakes, water, and a water-soluble binder on the hole transport layer, and drying. The metal electrode comprises silver.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: (Acetyloxy)(hydroxy)alumanyl acetate is added in an amount between 0.5 wt.% and 6 wt.% compared with zinc acetate dihydrate, preferably in an amount of 1-1.5 wt.%. Zinc acetate and (acetyloxy)(hydroxy)alumanyl acetate are mixed in water. A wetting agent is further mixed. The wetting agent is Zonyl FSO-100 (RTM: 2-(perfluoroalkyl)ethanol) (CAS No. 65545-80-4) or Triton X-100 (RTM: polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether) (CAS No. 9002-93-1), preferably Zonyl FSO-100 (RTM: 2-(perfluoroalkyl)ethanol). The content of wetting agent in the ink is between 0.5 wt.% and 7.5 wt.%, preferably 1-3 wt.% of Zonyl FSO-100 (RTM: 2-(perfluoroalkyl)ethanol), or between 0.5 wt.% and 25 wt.%, preferably 9 wt.% of Triton X-100 (RTM: polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether). The ink contains zinc acetate dihydrate (0.1 g/l in water), (acetyloxy)(hydroxy)alumanyl acetate (1.5 wt.%), and Zonyl FSO-100 (RTM: 2-(perfluoroalkyl)ethanol) (1-3 wt.%).    TECHNOLOGY FOCUS - POLYMERS - Preferred Method: An active layer is formed by applying a coating ink comprising a light-harvesting polymer and an electron acceptor to the electron transport layer, and drying the coating ink layer. The active layer comprises poly(3-hexylthiophene) and (6,6)-phenyl-61C-butyric acid methyl ester (PCBM). The coating ink layer is dried and treated to convert the soluble precursor into a light harvesting polymer which is insoluble in the solvent of the coating ink. Preferred Composition: The coating ink used for forming active layer comprises a precursor of light harvesting polymer, fullerene, tetrahydrofuran, alcohol, and water. The alcohol is isopropanol. The precursor of light harvesting polymer is (2,2')bithiophenyl-4-carboxylic acid 3-(2,3-dihydroxy-propoxy)-1,1-dimethyl-propyl ester compound of formula (I). The fullerene is PCBM.n=not defined.N.B: n is not defined.