TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The inorganic semiconductor nanoparticles comprise zinc oxide, titanium dioxide, cadmium sulfide or cadmium. The material of cathode is metal, metal oxide, or graphene/its derivatives.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The electron acceptor material is C-60, C-70, their derivatives, or inorganic semiconductor nanoparticles. The C-60 is (6,6)-phenyl-C61-methyl butyrate (PC61BM) or (6,6)-phenyl-C71-methyl butyrate (PC71BM). The polar solvent is alcohol, water, or mixed solvent of alcohol and water.    TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The material of the flexible substrate is polyimide, polyethylene glycol terephthalate, polyethylene terephthalate, polyethylene naphthalate or other polyester material, and metal, its alloy or stainless steel film. The polar group- or ionic group-containing conjugated polymer is of formula: -(-(A)x-(B')y-(C')z-)n- (I). The active layer comprises an electron donor material and electron acceptor material. The electron donor material is conjugated polymer or organic low-molecular semiconductor material, preferably polythiophene, polyphenylene, polyfluorene, carbazole, thiophene pyrrole or their derivatives.x=0.5-1;y+z=0-0.5;x+y+z=l;n=1-300;A=polar conjugated unit comprising group chosen from fluorine group of formula (i), benzene group of formula (ii), spiral-p-benzene group of formula (iii) or carbazole group of formula (iv);B'=nonpolar conjugated unit comprising group chosen from fluorine group of formula (v), benzene group of formula (vi), spiral-p-benzene group of formula (vii) or carbazole group of formula (viii);R1,R2=amino, quaternary ammonium salt group, nitrile group, carboxy, sulfonic acid group or phosphoric acid group;R3,R4=H, 1-20C alkyl or 1-20C alkoxy;R3a,R4a=H or 1-20C alkyl;C'=sulfur-, silicon-, nitrogen- or selenium-containing aromatic heterocyclic unit of formula (a) or (b), benzothiazole (selenium) oxadiazole or its derivative of formula (c), quinoline/its derivative of formula (d) or (e), polythiophene/its derivative of formula (f), (g) or (h), selenophen/its derivative of formula (j), (k) or (l), quinoxaline derivative of formula (m), (n), (o) or (p), or silole derivative of formula (q), (r) or (s);X=S or Se;R5-R8=H or 1-10C alkyl;andR11,R12=H, 1-10C alkyl or phenyl.