TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The electron acceptor layer comprises a metal oxide, titania. The first electrode is indium tin oxide and the second electrode is gold.    TECHNOLOGY FOCUS - POLYMERS - Preferred Process: The process further comprises forming the electron acceptor layer on a substrate comprising the first electrode; forming the electron donor layer on the electron acceptor layer; and forming the second electrode on the electron donor layer.Preferred Components: (A) has been annealed by heat treatment. The temperature of the heat treatment is above the glass transition temperature of the polymer, preferably 70-280degreesC. (A) is the electron donor layer. (A) is a polyarylene, poly(arylene-vinylene) or a poly(arylene-acetylene), preferably poly(2-(2-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene). (A) is a polymer comprising monomer units of formula (-(-X((A)a)((B1)a)-)-).X = 6-14C arylene, 6-14C arylene-vinylene or 6-14C arylene-acetylene units;A = group of formula (-(L)l-EWG);EWG = electron-withdrawing group;L = spacer group such as 6-14C arylene, (6-14C arylene)-vinylene, (6-14C arylene)-acetylene, 5-10-membered heteroarylene, (5-10-membered heteroarylene)-vinylene or (5-10-membered heteroarylene)-acetylene groups, where the arylene and heteroarylene moieties are optionally substituted by 1-10C alkyl, 1-10C alkoxy or EWG groups;B1 = group of formula (-(L1)m-EDG);EDG = electron-donating group;a, b = 1-3;l, m = 0-10; andL1 = spacer group such as 6-14C arylene, (6-14C arylene)-vinylene, (6-14C arylene)-acetylene, 5-10-membered heteroarylene, (5-10-membered heteroarylene)-vinylene or (5-10-membered heteroarylene)-acetylene groups, where the arylene and heteroarylene moieties are optionally substituted by 1-10C alkyl, 1-10C alkoxy or EDG.Provided that: when l is greater than zero, EWG is attached to an arylene, heteroarylene, vinylene or acetylene moiety of L; when m is greater than zero, EDG is attached to an arylene or heteroarylene moiety of L1; and l and m are not both zero. EXAMPLE - A nanoporous layer of titanium dioxide was formed on pre-cleaned patterned indium tin oxide/glass (20 Omega/sq) and sintered for one hour at 450degreesC. This procedure was repeated twice. Then the polymer films (containing poly(2-(2-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene) with a molecular weight of 513,000 g.mol-1) (approximately 30-60 nm thick) were deposited on top of the titanium dioxide layer by spin coating from two chlorobenzene solutions with a different concentration (4.6 and 5.5 mg.ml-1, respectively) at a rate of 2,000 rpm and thermally evaporated through a shadow mask of a 45 nm thick gold layer to give the photovoltaic device.