Photoluminescent energy transfer was investigated in conjugated polymer-fluorophore blended thin films. A pen-tiptycene-containing poly(phenyleneethynylene) was used as the energy donor, and 13 fluorophores were used as energy acceptors. The efficiency of energy transfer was measured by monitoring both the quenching of the polymer emission and the enhancement of the fluorophore emission. Near-infrared emitting squaraines and terrylenes were identified as excellent energy acceptors. These results, where a new fluorescent signal occurs in the near-infrared region on a completely dark background, offer substantial possibilities for designing highly sensitive turn-on sensors. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3382-3391, 2010