Energy transfer-enhanced external power conversion efficiency in blended polymeric thin film solar devices

Abstract

In this paper, the spectral and electrical properties of a conjugated polymer poly [(9, 9-dioctyl-2, 7-divinylenefluorenylene)-alt-co-(1, 4-phenylene)] (PFO–MEH–PPV) with poly[3-(2-ethyl-isocyanato-octadecanyl) thiophene] (PECOD) in thin films have been studied. First, PFO–MEH–PPV and PECOD were dissolved in tetrahydrofuran and chloroform respectively for different concentrations. These solutions were deposited on glass substrates to form thin films with different thicknesses. The absorbance and photoluminescence spectra for each individual pure polymer were recorded and contrasted with those for blended conjugated polymer’s films to determine the effect of blending on the absorption and photoluminescence. Finally, we present a study on the processing and characterization of organic solar cells fabricated by spin coating pure PFO–MEH–PPV, PECOD and their blend as the organic active layer onto indium tin oxide layer (150 nm), followed by the evaporation of silver cathode (110 nm). The current–voltage characteristics of these cells were determined and external quantum efficiency. Upon blending the two polymers in solid forms, it could be seen that the efficiency (6.25%) for the cells based on a blend layer is higher than the ones without blending (4.4%). Finally, we demonstrated here that the combination/blending of conjugated polymers has resulted in optimized solar device function, with reasonably quantum efficiency higher than 10%.