Figure 1

(a) Molecular structures of P3HT, PBT1, PBDTBDD-C-T, PBDTBDD, PC₆₀BM, PC₇₀BM and ZrAcac; (b) Device structure of the polymer solar cells; (c) Schematic energy diagram of the materials involved in the PSCs; (d) UPS spectra of a-ZrAcac on ITO substrate.