Spin- and Spray-Deposited Single-Walled Carbon-Nanotube Electrodes for Organic Solar Cells

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 HNO3 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 Omega sq(-1) are obtained at reasonable transmission, for example, 128 +/- 2 Omega sq(-1) at 90% for DCE, 57 +/- 3 Omega sq(-1) at 65% for H2O:SDS, and 68 +/- 5 Omega sq(-1) at 70% for H2O:SDBS. Solar cells are fabricated by successively coating the SWCNT films with poly(3,4-ethylenedioxythiophene):poly(styrene 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, H2O:SDS and H2O:SDBS, with the first two being at a virtual parity with reference devices using ITO-coated glass as the anode (2.3%).