Long-lived excited state of C60 in C60/phthalocyanine heterojunction solar cell

Abstract

The photovoltaic properties of ITO (indium tin oxide)/C60/H2(pc), (pc=phthalocyanine)/Au sandwich solar cells are investigated. The cell prepared at a higher vacuum (1×10−6 Torr) shows an open-circuit photovoltage (VOC) of 0.18 V, a short-circuit photocurrent (JSC) of 89 μA cm−2, a fill factor (ff) of 0.25, and an energy conversion yield (η) of 0.03% when illuminated by white light with 12.5 mW cm−2 intensity. The photocurrent action spectra of the cell reveal that photocurrent is generated at C60/H2(pc) interface with diffusion of C60 excitons because the excited state of C60 has a relatively long lifetime, while the cell prepared at a lower vacuum (3×10−5 Torr) shows a much smaller photocurrent (JSC=1.4 μA cm−2) because oxygen in C60 acts as carrier traps and increases the resistance of C60.