TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Device: The photoactive layer is separated by the transport layer before, during and after deposition of the contact layers. The optical path of incident light in the photoactive layer can be extended by a light trap, preferably a doped transport layer with smooth interface to the i-layer and periodically microstructurized interface to the contact area; and/or the device is formed on a periodically microstructurized substrate, with doped transport layer applied to ensure homogeneous function on its entire area. The i-layer has several layers with various absorption spectra. The device may have a second pi-, ni- or pin-diode structure with similar band gap and transmission properties. In this case, the i-layers of individual structures have the same optical absorption and are optically thin, so that they transmit not less than 50% of the light at the absorption maximum or have different optical absorption spectra, which mutually complement one another. There may be at least 3 structures comprising several optical thin i-films with the same absorption spectrum and also i-films, with different, complementary absorption spectra. The n- or p-layer near the junction between 2 structures is doped. Between the p-layer of the n-th structure and the n-layer of the (n+1)-th structure, the device has layer(s) of metal, salt or (in)organic material and a (semi)transparent contact for individual contacting of single structures. Preferred layers include doped layer(s) of (in)organic semiconductor material; (semi)transparent layer(s) of metal, salt or other inorganic material, preferably TCO (transparent conductive oxide) layer(s); and layer(s) of nanoclusters of metal, salt or (in)organic material. The device has one or more light traps. The contacts consist of highly transparent ITO (indium tin oxide), other transparent and conductive materials, e.g. ZnO (zinc oxide), ZnO:aluminum (Al), conductive polymer, especially PEDOT:PSS (poly(3,4-ethylenedioxythiophene)-poly(styrene-sulfonate)), or metals as semitransparent layer. The thickness of the layers, especially the i-layers, is selected so that all structures yield the same photo-current with respect to the distribution of the optical field in the device. The thickness of the n- and/or p-layers is selected to optimize the position of the i-layer with respect to the field strength distribution of the optical field. The p-layer is a p-doped layer, the i-layer is undoped or only slightly doped compared with other layers, absorbs photons and generates current, so that it forms the photoactive layer, and the n-layer consists of n-doped layer(s). There may be a doping density gradient in the photoactive layer(s) or transport layer(s) so that the doping density in the transport layers decreases in the direction of the active layer. The photoactive layers, especially mixed layers, consist of organic materials or (partly) of inorganic materials. Preferred dopants are inorganic materials, especially an alkali metal. The charge transport layers consist (partly) of inorganic material. Organic acceptor molecules are used for p-doping of the hole transport layers.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Materials: Organic acceptor molecules used for doping the hole transport layers are selected from quinones, tetracyanoquinodimethane (TCNQ derivatives, e.g. F4-TCNQ), dicyanoquinoquinodiimide (DCNQI derivatives) and corresponding derivatives of higher quinones (naphtho- and anthraquinone derivatives). Suitable host materials for the p-transport layers include derivatives of tetraphenyldiamine (TPD), especially those with ionizing energy reduced by electron-positive substituents, e.g. methoxy or methyl groups, and their spiro-derivatives; triphenylamine derivatives, especially derivatives of tris(diphenylamino)-triphenylamine (TDATA), triaminophenyl derivatives and triphenylbenzene derivatives; porphyrins or phthalocyanines; and perylene or terrylene derivatives. Suitable host materials for the n-transport layers include derivatives of perylene- or naphthalene-tetracarbodiimide (PTCDI, NTCDI), dianhydride (PTCDA, NTCDA) or -bisimidazole (PTCBI, NTCBI); fullerenes, e.g. C60 or C70 and their derivatives; phthalocyanines or porphyrins with electron affinity increased by electronegative groups, e.g. fluorine (F) or chlorine (Cl); quinones; and oxadiazole derivatives.    TECHNOLOGY FOCUS - POLYMERS - Preferred Materials: Suitable host materials for the p-transport layers include oligomers with donor character obtained by using thiophene rings, especially oligothiophenes; and derivatives of oligo-para-phenylene-vinylene (OPPV). Suitable host materials for the n-transport layers include oligomers with electron affinity increased by substituents, e.g. F, Cl, CF3, CN etc., e.g. perfluorinated oligophenyls.