New soluble porphyrin bearing a pyridinylethynyl group as donor for bulk heterojunction solar cells

Bulk heterojunction solar cells were fabricated using the blend films of a porphyrin bearing pyridinylethynyl group (POR) as electron donor and PC60BM or PC70BM as electron acceptor. Photoluminescence measurement of the blend films of POR with fullerene derivatives indicated that charge transfer was possible between POR and fullerene derivatives. The solution processed bulk heterojunction solar cells using the blend of POR with PC60BM and PC70BM exhibit overall power conversion efficiency (PCE) of 1.96% and 2.54%, respectively. The PCE of the BHJ solar cell has been further improved up to 3.27% when thermally annealed POR:PC70BM was used as active layer, which is attributed mainly to the increase in short circuit current. The increase in J(sc) is attributed to the enhanced crystallinity of the blend (particularly POR) and efficient pi-electron conjugation of POR, resulting to an improvement in hole mobility, leading to more balance charge transport. The PCE of the device based on as cast POR:PC70BM has been further improved up to 4.06% when DMF treated PEDOT:PSS buffer layer was used. (C) 2013 Elsevier B.V. All rights reserved.