Influence of Donor and Acceptor Mass Ratios on P3HT:PCBM Film Structure and Device Performance

Abstract

Organic bulk heterojunction photovoltaic devices based on poly(3-hexylthiophene)(P3HT,donor) and [6,6]-phenyl-C61-butyric acid methyl ester(PCBM,acceptor) were fabricated using solvent annealing treatment.The nanoscale morphology and structure of the P3HT:PCBM blend films were characterized by UV-Vis absorption spectroscopy(UV-Vis),atomic force microscopy(AFM),and X-ray diffraction(XRD) analyses.In addition,the AFM images were processed using the entropyfilt method.The performances of the P3HT:PCBM devices with different mass ratios were measured,having a structure of indium tin oxide(ITO)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)/P3HT:PCBM/aluminium(Al).The results showed that the crystallinity of the P3HT polymer can be disturbed by the relative amount of PCBM molecules.The 1:1(mass ratio) blend film possessed the greatest absorption width by UV-Vis absorption,as well as good phase separation and a high level of crystallinity,providing the best device performance(2.77%).This study indicates that the donor and acceptor mass ratios do have an influence on the nanoscale morphology and structure of the blend films,which can in turn affect the device performance.