Raman study of the interaction between regioregular poly(3-hexylthiophene) (P3HT) and transition-metal oxides MoO3, V2O5, and WO3 in polymer solar cells

⿢Raman spectra of ITO/P3HT/anode buffer material (MoO3, V2O5, or WO3) were obtained.⿢The Raman spectrum of ITO/MoO3/P3HT was also obtained.⿢Positive polarons were formed in a P3HT film upon MoO3, V2O5, or WO3 deposition.⿢The number of positive polarons increased in the order WO3 < V2O5 < MoO3.⿢Polaron electronic energy levels distribute around the Fermi level of an electrode.