The effects of mixture ratios of CuPc:C 60 in nanostructured organic hybrid planar–mixed heterojunction photovoltaic cells

Efficient organic hybrid planar–mixed heterojunction photovoltaic cells based on copper phthalocyanine (CuPc) and fullerene (C60) were fabricated. This structure, in addition to the high efficiency in exciton diffusion of a mixed heterojunction, has low resistance in charge transporting of a planar heterojunction. The effects of different CuPc:C60 mixing ratios in two stages and by varying the CuPc and C60 thicknesses, respectively, were investigated. Also, we illustrate the charge transport mechanisms and specify the charge injection models for the cells. For the optimized cell, trap-charge-limited current (TCLC) model was dominant. MoO3 is one of the common materials as anodic buffer layer which is used for modifying the ITO electrode and improving the charge extraction. According to the AFM results, after depositing MoO3 layer on ITO, the surface root mean square (RMS) roughness decreases from 8.31 to 4.14 nm. Optimal thickness for both CuPc and C60 layers was obtained 20 nm. Finally, the greatest value in power conversion efficiency was achieved 3.81% using the 1:1 CuPc:C60 mixing ratio. Moreover, short-circuit current density (Jsc), fill factor (FF), and open-circuit voltage (Voc) for this optimized cell were found 10.21 (mA/cm2), 0.64 (V), and 0.58, respectively.