Optimal hole extraction performance in MoOx-incorporated PEDOT:PSS films for organic photovoltaics

We propose a hole extraction system based on the metal-like poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) blended with MoOx. Tuning the volume ratio of MoOx to PEDOT:PSS, the conductivity increases ten times, compared to that of pristine PEDOT:PSS film. The efficient charge recombination and generation characteristics between MoOx with PEDOT:PSS are argued as the increase. No additional absorption peak due to the charge transfer in the hole transport layer implies that the system does not follow the P-type doping technique. The use of MoOx-mixed PEDOT:PSS thin film as the hole extraction layer for the poly{4,8-bis[5-(2-ethylhexyl)-thiophen-2-yl]benzo[1,2-b;4,5-b’]dithiophene-2,6-diyl-alt-[4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene]-2-carboxylate-2-6-diyl} (PTB7-Th) and [6,6]-phenyl C70-butyric acid methyl ester (PC[70]BM)-based organic solar cells is found to increase the short circuit current density and fill factor of the device concomitant, and the power conversion efficiency increases from 6.7 to 8.1% when the MoOx mixing ratio is 3%. The improved hole extraction performance of MoOx-mixed PEDOT:PSS thin film would be beneficial for potential applications in organic electronic devices.