A ternary morphology facilitated thick-film organic solar cellElectronic supplementary information (ESI) available. See DOI: 10.1039/c5ra17268c

Employing a thick active layer for organic photovoltaic (OPV) devices, holding great promise for enhanced light absorption and providing robust, pinhole-free films for large-scale fabrication, remains a great challenge. In this work, we propose a new route for fabricating thick-film OPV devices through a ternary bulk heterojunction system by combining a fullerene derivative with one high-crystallinity polymer and one high power conversion efficiency (PCE) polymer. As a demonstration, P3HT:PTB7:PC 71 BM ternary cells were fabricated, showing that they could maintain higher PCE with a thick active layer than both binary counterparts could. Synchrotron based grazing-incidence X-ray scattering results indicated that the ternary morphology gave rise to a smaller intermixing domain size and a favorable molecular orientation, which should be beneficial to charge separation and transport. We applied a ternary morphology to enhance light harvesting of a thick-film polymer solar cell.