Contribution of fullerene photocurrent generation to organic solar cell performance

Light harvesting is the critical first step in the generation of photocurrent in solar photovoltaic devices. In the case of organic photovoltaic devices based on binary blends of conjugated polymer donors and fullerene acceptors, light harvesting can occur both at the conjugated polymer and in the fullerene components. As such, both elements in the blend contribute to the generation of photocurrent. In this paper, optical modeling is used to compare the relative light harvesting of the polymer and fullerene components for binary active layers consisting of poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C₆₁ -butyric acid methyl ester, P3HT:[6,6]-phenyl-C₇₁ -butyric acid methyl ester, and P3HT:indene-C₆₀ bisadduct. We show that the relative contribution of light harvesting and photocurrent generation by the fullerene component is greater than that previously considered and can rise to as high as 30% of the total photocurrent generated by the binary blend system.