Fabrication and Characterization of Conjugated Polymer P: PCBM Bulk Heterojunction Solar Cells

A conjugated polymer Poly-2-(2-{, 4- divinyl -2, 5-bis (hexyloxy) -benzene}-4-nitrophenyl) acrylonitrile (P) is used as a donor. Its photophysical, electrochemical and photovoltaic properties have been investigated. A thin film of P showed a long wave absorption maximum at 460 nm and an optical band gap of 2.15 eV. Bulk heterojunction (BHJ) solar cell based on this new polymer was fabricated with device structures of ITO/PEDOT: PSS/polymer: PC₆₁BM (1:1)/Al. The photovoltaic properties of the polymer have been evaluated under illumination intensity of 100 mW/cm². The BHJ showed power conversion efficiency (PCE) up to 1.13%. The PCE has been further improved up to 1.60% and 2.10% after solvent and thermal annealing of the P: PCBM layer. The solvent and thermal annealing allows not only a broad absorption but also tuning of the inter energy level leading to a higher short circuit current (J_sc) and open circuit voltage (V_oc). The best performance device exhibited a PCE of about 2.10% with the thermally annealed solvent treated P: PCBM photoactive layer.