A combined optical and morphological study of 2,5-bis(dodecanoxy) phenyleneethynylene-butadiynes films for oLEDs

Abstract Thin films of a series of symmetrical 2,5-bis(dodecanoxy)phenyleneethynylenes, bearing a butadiyne central group and 4, 6 and 8 phenyleneethynylene moieties, were prepared by spin coating. In general, narrower and red shifted peaks are observed in both absorption and emission spectra with respect to the solutions previously reported, however, the fluorescence quantum yield was quenched. All of these features are explained with the planarization of the conjugated chain, and intra/intermolecular interactions, as supported by spectroscopic aggregation studies and by atomic STM and microscopic AFM characterization. By cathodoluminescence spectroscopy, hot charged states are found that may also affect the fluorescence and electroluminescence properties. From the series, the latter were studied for the hexamer 6DAc for which an oLED with configuration ITO/PEDOT:PSS/6DAc/Al was constructed in ambient conditions, giving a threshold voltage of 11 V and quantum yield of 0.031 ph/e%, of the same order of other phenyleneethynylenes or phenylenebutadyines devices.