Series of polar alcohol-additives assisted improvement in the PEDOT:PSS film property and bulk-heterojunction organic solar cell performance

Doping poly(3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) by polar solvent is a promising approach to decrease the resistivity of pristine PEDOT:PSS film. In this work, properties of doped PEDOT:PSS films by a series of alcohol additives, including ethanol, glycerol, meso-erythritol, xylitol, and D-sorbitol, are comparatively studied for the first time. The absorption spectra, surface morphology, solvent contact angle, hole mobility, work function, and carrier transport properties via Hall measurement of these doped films were systematically investigated to find out the dopant dependent PEDOT:PSS film property. Then these low-resistivity PEDOT:PSS films were applied as the hole transport layer in 20 wt% poly(diketopyrro lopyrrole-terthiophene) (PDPP3T) based bulk heterojunctions (BHJs), and the highest power conversion efficiency (PCE) of 3.74% was achieved for the meso-erythritol doped PEDOT:PSS based BHJ, which is 21% higher than that (3.09%) of the pristine PEDOT:PSS based BHJ. Finally, the performance of all six BHJs is significantly improved by using lithium fluoride instead of bathocuproine, and the PCE for the meso-erythritol doped PEDOT:PSS based BHJ achieves 4.86%. Among these alcohol additives, meso-erythritol and D-sorbitol depict the optimum doping effect. Our results give important guidance to develop alcohol-additive doped PEDOT:PSS films in organic optoelectronic devices.