Three dithiafulvene-based metal -free organic sensitizers all using pyridine as the acceptor but with different pi-bridges of phenyl (DTF-Pyl), thienyl (DTF-Py2) and phenyl-thienyl (DTF-Py3) have been designed, synthesized and used as photosensitizers for dye -sensitized solar cells (DSCs). Introducing thienyl unit into the pi-bridge, as well as extension of the it -bridge can dramatically improve their light harvesting ability and suppress the electron recombination, thus uplifting the performance of DSCs. The overall power conversion efficiency of DSC based on DTF-Py3 shows the highest efficiency of 2.61% with a short-circuit photocurrent density of 7.99 mA cm(-2), an open -circuit photovoltage of 630 mV, and a fill factor of 0.52, under standard global AM 1.5 solar light condition. More importantly, the long-term stability of the DTF-Py3 based DSCs under 500 h light-soaking has been demonstrated. (C) 2017 Elsevier B.V. All rights reserved.