Cathode buffer layers based on vacuum and solution deposited poly(3,4-ethylenedioxythiophene) for efficient inverted organic solar cells

Vacuum and solution processed versions of poly(3,4-ethylenedioxythiophene) (PEDOT) are used as cathode interlayers in inverted organic photovoltaic cells comprising tetraphenyldibenzoperiflanthene as the electron donor and C-60 as the electron acceptor. Chemical treatment of the as-deposited PEDOT layers with tetrakis(dimethylamino) ethylene or cesium carbonate reduces the work function by up to 0.8 eV. Inserting these PEDOT layers at the indium tin oxide cathode results in improved electron collection and efficiencies of up to 2.3 +/- 0.2%, approaching the 3.2 +/- 0.3% of the conventional device. This illustrates the potential for efficient polymer cathode materials and inverted device architectures compatible with either solution or vacuum processing. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4709481]