Organic photovoltaic cells with copper (Ⅱ) tetra-methyl substituted phthalocyanine

Efficient heterojunction organic photovoltaic (OPV) cells are fabricated based on copper tetra-methyl phthalocyanine (CuMePc) as donor and fullerene (C₆₀) as acceptor. The power conversion efficiency of CuMePc/C₆₀ OPV cell (2.52%) is increased by 88% compared with that of the non-peripheral substituted copper phthalocyanine (CuPc)/C₆₀ OPV cell (1.34%). The introduction of methyl substituent leads to stronger π–π interaction of CuMePc (～ 3.5 Å) than that of CuPc (～ 3.8 Å). The efficiency improvement is attributed to the enhanced carrier mobility of CuMePc thin film (1.1×10^-3 cm²/V·s) and better film morphology by introducing methyl groups into the periphery of CuPc molecule.