Donor−Acceptor Molecule as the Acceptor for Polymer-Based Bulk Heterojunction Solar Cells

We fabricated polymer-based bulk heterojunction (BHJ) solar cells using a donor−acceptor (D-A) molecule N -propyl-3,6-bis[2-(3-dicyanomethylene-5,5-dimethylcyclohex-1-enyl)vinyl]carbazole (PDHC) as the acceptor. The strong photoluminescence (PL) quenching of poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) when mixed with PDHC means that efficient charge transfer has happened between MEH-PPV and PDHC. We used MEH-PPV and poly (3-hexylthiophene) (P3HT) as the donors and PDHC as the acceptor to fabricate BHJ solar cells. The cells with the structure of ITO/PEDOT/polymer:PDHC/LiF/Al exhibited a power conversion efficiency (PCE) about 0.2% under 100 mW/cm 2 white light illumination. The open-circuit voltages ( V oc s) of 1.14 V of the cells based on MEH-PPV:PDHC and about 0.76 V of the cells based on P3HT:PDHC were achieved, which are higher than the V oc s of the corresponding solar cells with phenyl-C-butyric acid methyl ester (PCBM) as the acceptor. In comparison with the cells based on PCBM, the relatively lower PCE of solar cells based on PDHC is due to its low electron mobility of 1.15 × 10 −5 cm 2 V −1 S −1 estimated by the space charge limited current method.