Improvement in power conversion efficiency by blending of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) into poly(3-hexylthiophene):phenyl-C 61-butyric acid methyl ester active layer

The improvement in power conversion efficiency (PCE) by the addition of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) into regioregular poly(3-hexylthiophene) (P3HT) and phenyl-C 61-butyric acid methyl ester (PCBM)-based bulk heterojunction (BHJ) organic photovoltaic (OPV) devices was investigated. The addition of PEDOT:PSS into the P3HT:PCBM active layer was found to promote a significant enhancement of the fill factor, which ultimately increased the PCEs of the corresponding OPV devices, although the exciton generation rates of the BHJ layers were virtually the same, as observed by UV-Vis absorption spectra. Therefore, we conclude that the reduction of internal series resistance (R S) was the most crucial reason for the PCE improvement by the addition of PEDOT:PSS.