Open-circuit voltage of ternary blend polymer solar cells

We have studied the different dependence of open-circuit voltage ( V OC ) on blend compositions in ternary blend solar cells based on poly(3-hexylthiophene) (P3HT) and the other two materials selected from phenyl-C 61 -butyric acid methyl ester (PCBM), indene-C 60 bisadduct (ICBA), and silicon phthalocyanine bis(trihexylsilyl oxide) (SiPc). For P3HT/PCBM/ICBA ternary blend solar cells, the V OC monotonically increased with increasing ICBA fraction as reported previously. On the other hand, the V OC in P3HT/ICBA/SiPc solar cells slightly decreased from 0.84 to 0.82 V at a SiPc fraction of 5% and then was kept constant independently of the SiPc fraction up to 50%. For P3HT/PCBM/SiPc solar cells, the V OC was almost independent of the SiPc fraction up to 45%, and then abruptly increased from ∼0.55 to 0.82 V at a SiPc fraction of 50%. We discuss these different compositional dependences of V OC in terms of the energetics and the blend morphology in ternary blend solar cells.