Solution-Processed Bulk-Heterojunction Solar Cells containing Self-Organized Disk-Shaped Donors

摘要

Two molecular disks 1 and 2 composed of a central pyrene core, four oligothiopenes, and peripheral alkyl chains were synthesized and characterized with respect to c optical and redox properties in solution and in solid films. It was found that the lowest unoccupied molecular orbital (LUMO) energy levels of 1 and 2 were ideal for achieving efficient electron transfer to fullerene derivatives PC_(60)BM and PC_(70)BM, and that 1 and 2 can function as electron donor components in solution-processed bulk-heterojunction (BHJ) solar cells. Disk-shaped molecules 1 and 2 organized ordered structures through intermolecular π— π interactions as monitored by temperature-controlled polarized optical microscope (TPOM), differential scanning calorimetry (DSC), and powder X-ray diffraction (XRD). Solution-processed BHJ solar cells using 1 or 2 as electron donor materials and fullerene derivatives as acceptor materials were fabricated and investigated. The oligothiophene lengths were reflected in the performance characteristics of solar cell devices fabricated using disk-shaped donors 1 and 2. Power conversion efficiency (PCE) of 2.6% was achieved for small-molecule BHJ solar cells containing self-organized crystals of 2 in the active layer under one sun condition.