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Organic bulk-heterojunction solar cells using thin-film single-walled carbon-nanotube (SWCNT) anodes deposited on glass are reported. Two types of SWCNT films are investigated: spin-coated films from dichloroethane (DCE), and spray-coated films from deionized water using sodium dodecyl sulphate (SDS) or sodium dodecyl benzene sulphonate (SDBS) as the surfactant. All of the films are found to be mechanically robust, with no tendency to delaminate from the underlying substrate during handling. Acid treatment with HNO 3 yields high conductivities >1000 S cm ―1 for all of the films, with values of up to 7694 ± 800 S cm ―1 being obtained when using SDS as the surfactant. Sheet resistances of around 100 Ω sq ―1 are obtained at reasonable transmission, for example, 128 ± 2 Ω sq ―1 at 90% for DCE, 57 ± 3 Ω sq ―1 at 65% for H 2 O:SDS, and 68 ± 5 Ω sq ―1 at 70% for H 2 O:SDBS. Solar cells are fabricated by successively coating the SWCNT films with poly(3,4-ethylenedioxythiophene) : p o l y(st y rene sulphonate) (PEDOT:PSS), a blend of regioregular poly(3-hexylthiophene) (P3HT) and 1-(3-methoxy-carbonyl)-propyl-1-phenyl-(6,6)C 61 (PCBM), and LiF/Al. The resultant devices have respective power conversions of 2.3, 2.2 and 1.2% for DCE, H 2 O:SDS and H 2 O:SDBS, with the first two being at a virtual parity with reference devices using ITO-coated glass as the anode (2.3%).

We use electromodulation spectroscopy and modeling studies to probe the electric-field distribution in polyfluorene-based polymer light-emitting diodes containing poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate). The bulk internal field is shown to be zero under ordinary operating conditions, with trapped electrons close to the anode fully screening the bulk semiconductor from the external field. The effect has far-reaching implications for the understanding and optimization of organic devices.