Indium Tin Oxide-Free Small Molecule Organic Solar Cells Using Single-Walled Carbon Nanotube Electrodes

We demonstrated single-walled carbon nanotubes (SWNTs) electrode-based small molecule organic solar cells (OSCs) using diketopyrrolopyrrole donor, DPP(TBFu) 2 as an electron donor with [6,6]-phenyl-C61-butyric acid methyl ester (PC 61 BM) as an electron acceptor. SWNT films with 60% transmittance (at 550 nm) were dry-transferred onto glass substrates to replace conventional indium tin oxide (ITO) electrodes. In order to improve the conductivity of the SWNT electrodes, MoO x thermal doping was applied followed by spin coating of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) to enhance doping and electrode blocking function. The indium-free devices showed a power conversion efficiency (PCE) of 1.00% while ITO-based devices showed a PCE of 3.79%.