Fabrication of silver nanowire transparent electrodes using electrohydrodynamic spray deposition for flexible organic solar cells

Abstract

Fabrication of a flexible organic solar cell is demonstrated with an anode that is free of tin-doped indium oxide (ITO) by electrohydrodynamic (EHD) spraying of silver nanowires (Ag NWs). This methodology is applicable to fabricate patterned Ag NW thin-film electrodes for organic solar cells (OSCs). By optimizing the spray parameters and post-processing conditions, transparent electrodes with sheet resistances of ∼11 Ω sq-1 (on glass) and ∼20 Ω sq-1 (on polyethylene terephthalate, PET) and DC to optical conductivities of ∼70 (on PET) can be obtained at an optical transmittance of ∼80%. Bulk heterojunction OSCs are demonstrated with patterned Ag NW films serving as bottom transparent anodes on both glass substrates and flexible PET substrates. The photoactive layers are based on low band-gap polymers, poly[(4,8-bis-(2-ethylhexyloxy)-benzo[1,2-b;4.5-b′] dithiophene)-2,6-diyl-alt-(4-(2-ehtylhexanoyl)-thieno[3,4-b]thiophene)]-2, 6-diyl] and phenyl-C61-butyric acid methyl ester. Under AM 1.5 illumination, fabricated cells have high power conversion efficiencies of 5.27% (on glass) and 3.76% (on PET). This study indicates that a Ag NW electrode prepared by EHD spraying can serve as an alternative to the ITO electrode, which also enables its potential application in practical and flexible OSCs. © 2013 The Royal Society of Chemistry.