TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The common building block constitutes an electron donating unit of the donor materials. The common building block is at each occurrence, and it is fused heterocyclics of formulae (I)-(X). The donor material comprises an electron withdrawing building block. The first donor material and the second donor material each comprise an electron withdrawing building block, and the electron withdrawing building block of the first donor material has more electron withdrawing capability than the electron withdrawing building block of the second donor material. The first donor material comprises an electron withdrawing building block of fused heterocyclics of formulae (XI)-(XX) and the second donor material comprises an electron withdrawing building block of fused heterocyclics of formulae (XXI)-(XXX). In the photovoltaic cell, at least one of the donor materials is a polymer or an oligomer, and at least two of the donor materials are fused sulfur-containing tricyclic compounds of formula (KP179, KP252, KP184, KP143 or KP155). The acceptor material comprises a compound of fullerene, substituted fullerene, fullerene derivatives, perylene diimide derivatives, benzo thiazole derivatives, diketo-pyrrolo-pyrrole derivatives, bi-fluorenylidene derivatives, pentacene derivatives, quinacridone derivatives, fluoranthene imide derivatives, boron-dipyrromethene derivatives, oxadiazoles, metal phthalocyanine and sub-phthalocyanine, inorganic nanoparticles, discotic liquid crystals, carbon nanorods, inorganic nanorods, polymers containing CN groups, and/or polymers containing trifluoromethyl. The substituted fullerene is phenyl-C60-butyric acid methyl ester, phenyl-C61-butyric acid methyl ester, and/or phenyl-C70-butyric acid methyl ester. The photoactive layer further comprises a dopant. The dopant is diiodo octane, octadecanethiol, and/or phenylnaphthalene. The solvent is organic solvent. The solvent comprises aliphatic hydrocarbons, chlorinated hydrocarbons, aromatic hydrocarbons, ketones, and/or ethers. Additional solvents which can be used include 1,2,4-trimethylbenzene, 1,2,3,4-tetra-methyl benzene, pentylbenzene, mesitylene, cumene, cymene, cyclohexylbenzene, diethylbenzene, tetralin, decalin, 2,6-lutidine, 2-fluoro-m-xylene, 3-fluoro-o-xylene, 2-chlorobenzotrifluoride, N,N-dimethylformamide, 2-chloro-6-fluorotoluene, 2-fluoroanisole, anisole, 2,3-dimethylpyrazine, 4-fluoroanisole, 3-fluoroanisole, 3-trifluoro-methylanisole, 2-methylanisole, phenetol, 4-methylanisole, 3-methylanisole, 4-fluoro-3-methylanisole, 2-fluorobenzonitrile, 4-fluoroveratrol, 2,6-dimethylanisole, 3-fluorobenzo-nitrile, 2,5-dimethylanisole, 2,4-dimethylanisole, benzonitrile, 3,5-dimethyl-anisole, N,N-dimethylaniline, ethyl benzoate, 1-fluoro-3,5-dimethoxy-benzene, 1-methylnaphthalene, N-methylpyrrolidinone, 3-fluorobenzo-trifluoride, benzotrifluoride, dioxane, trifluoromethoxy benzene, 4-fluorobenzotrifluoride, 3-fluoropyridine, toluene, 2-fluoro-toluene, 2-fluorobenzotrifluoride, 3-fluorotoluene, 4-isopropylbiphenyl, phenyl ether, pyridine, 4-fluorotoluene, 2,5-difluorotoluene, 1-chloro-2,4-difluorobenzene, 2-fluoropyridine, 3-chlorofluoro-benzene, 1-chloro-2,5-difluorobenzene, 4-chlorofluorobenzene, chloro-benzene, o-dichlorobenzene, 2-chlorofluorobenzene, and/or p-xylene, m-xylene, and/or o-xylene.R1-R4 = H, halo, 1-40C alkyl, 1-40C alkoxy, aryl, heteroaryl, 3-40C cycloalkyl, 3-40C heterocycloalkyl, CN, OR9, COR9, COOR9 or CON(R9R10);R9, R10 = H, 1-40C alkyl, aryl, heteroaryl, 3-40C cycloalkyl or 3-40C heterocycloalkyl;R11-R16 = H, halo, 1-40C alkyl, 1-40C alkoxy, aryl, heteroaryl, 3-40C cycloalkyl, 3-40C heterocycloalkyl, CN, OR17, COR17, COOR17 or CON(R17R18);R17,R18 = H, 1-40C alkyl, aryl, heteroaryl, 3-40C cycloalkyl or 3-40C heterocycloalkyl;R19-R24 = H, halo, 1-40C alkyl, 1-40C alkoxy, aryl, heteroaryl, 3-40C cycloalkyl, 3-40C heterocycloalkyl, CN, OR25, COR25, COOR25 or CON(R25R26);R25, R26 = H, 1-40C alkyl, aryl, heteroaryl, 3-40C cycloalkyl or 3-40C heterocycloalkyl;R = ethylhexyl; andn = not defined.