TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The donor layer comprises a donor material of photoactive semiconducting polymer-wrapped carbon nanotubes. The acceptor layer comprises an acceptor material of photoactive semiconducting polymer-wrapped carbon nanotubes. The photovoltaic device further comprises an exciton blocking layer provided between the acceptor layer and the second electrode or between the donor layer and the first electrode. The photoactive region comprises a first bulk heterojunction layer and a second bulk heterojunction layer. The first bulk heterojunction layer comprises photoactive semiconducting polymer-wrapped carbon nanotubes disposed within a first organic semiconductor material that is an electron donor type material with respect to the polymer-wrapped carbon nanotubes. The second bulk heterojunction layer comprises photoactive substantially semiconducting polymer-wrapped carbon nanotubes disposed within a second organic semiconductor material that is an electron acceptor type material with respect to the polymer-wrapped carbon nanotubes.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The organic semiconductor material in the bulk heterojunction layer is an electron acceptor type material with respect to the photoactive semiconducting polymer-wrapped carbon nanotubes. The photoactive semiconducting polymer-wrapped carbon nanotubes are semiconducting polymer-wrapped single-wall carbon nanotubes which: are wrapped with a photoactive polymer; and create excitons upon absorption of light at 400-1400 nm. The electron acceptor type organic semiconductor material is evaporated fullerene, (6,6)-phenyl C84 butyric acid methyl ester, copper hexadecafluorophthalocyanine, 3,4,9,10-perylenetetracarboxylic bis-benzimidazole, 3,4,9,10-perylene-tetracarboxylic acid dianhydride, poly(benzimidazobenzophenanthroline), 7,7,8,8-tetracyanoquinodimethane), or tetrafluorotetracyanoquinodimethane. The organic semiconductor material in the bulk heterojunction layer is an electron donor type material with respect to the photoactive semiconducting polymer-wrapped carbon nanotubes. The electron donor type organic semiconductor material is poly(2,5-bis(1,4,7,10-tetraoxaundecyl)-1,4-phenylenevinylene), poly(3-decyloxythiophene), copper phthalocyanine, 4,4'-bis(N-(1-naphthyl)phenylamino)biphenyl, pentacene or tetracene.