We investigated the effect of additives on the morphology of a poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b ]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT):(6,6)-phenyl C71-butyric acid methyl ester (PC71BM) blended onto a surface of poly (3, 4-ethylendioxythiophene): poly(styrensulfonate)(PEDOT:PSS) to form photoactive films. Films of PCPDTBT: PC71-BM bulk heterojunctions were prepared by spin-coating from a solution in chlorobenzene (CB) and were processed with and without the addition of 2%, 4%, and 6 vol% 1-chloro naphthalene (CN) or 1, 8-octanedithiol (ODT) as additives. For all samples, the PCPDTBT:PC71BM molar ratio was 1:2 (wt%), and the additives in 1 ml were prepared with a concentration of 30 mg of PCPDTBT:PC71BM. Optical absorption spectroscopy measurements of the films indicated shifts in the absorption peaks in the range from 500 -800 nm which was attributed to PCPDTBT. X-Ray diffraction (XRD) was used to investigate the nature of the molecular stacking in the polymer thin films. Topographic images which were obtained by using an atomic force microscope, of the PCPDTBT:PC71BM layers with 2 vol% ODT additive, were found to have the highest surface roughness. The best performing device shows a power conversion efficiency of 2.15% for a 2-vol% ODT additive.
Abstract. The organic semiconductors of poly(3-hexylthiophene) (P3HT), poly(3-octylthiophene)(P3OT), poly(3-dodecylthiophene) (P3DDT) and [6,6]-phenyl C 71 butyric acid methyl ester (PC71BM) were used to make active layers. The active layers of an organic thin film solar cell were fabricated by the P3HT/PC71BM, P3HT/P3OT/PC71BM and P3HT/P3DDT/PC71BM fluid, respectively. Compared with the performances, the performance of the organic solar cell fabricated by P3HT/P3OT/PC71BM thin film indicates the best. The open circuit voltage is 0.61 V. The short-circuit current density is 6.55 mA cm 2 . The fill factor is 0.51. The power conversion efficiency is 2.07%. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).
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