Bulk heterojunction solar cells based on two kinds of organic polymers and fullerene derivative

We report a study of the effect of the poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) on the organic solar cell based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction structure (BHJ). The most obvious effect of incorporating MEH-PPV in the P3HT:PCBM BJT solar cells was the increase in the open-circuit voltage (Voc) from 0.38 to 0.50 V. This result is interpreted in terms of the band structure of BHJ where the energy level difference between the highest occupied molecular orbital (HOMO) of the polymer (P3HT + MEH-PPV) and the lowest occupied molecular orbital (LUMO) of PCBM is increased. The highest power conversion efficiency of 1.12% under air mass 1.5 simulated solar illumination (100 mW/cm2) was achieved from the optimized amount of MEH-PPV. The spectral response of the P3HT:PCBM BHJ solar cells is influenced by the change of molecular packing structure (interchain spacing) of P3HT by incorporating MEH-PPV.