Tuning acceptor energy level for efficient charge collection in copper-phthalocyanine-based organic solar cells

We compare organic donor/acceptor heterojunction photovoltaic devices based on copper phthalocyanine (CuPc) as the donor and [6,6]-phenyl C-60 butyric acid methyl ester (PCBM) or buckminsterfullerene (C-60) as the acceptor. The effect of the two acceptors on open-circuit voltage and short-circuit current density is studied. Improved interface properties, optimal energy level matching, and more balanced charge transport are believed to be the reasons for better performance of CuPc/PCBM heterojunction device, in terms of photocurrent and fill factor. The energy conversion efficiency of the devices under AM1.5G solar illumination at 130 mW/cm(2) is improved to 1.18%, up from 0.74%.