INTERCHAIN PHOTOLUMINESCENCE IN POLY(PHENYLENE VINYLENE) DERIVATIVES

We calculate that in cyano-substituted poly(phenylene vinylene), CN-PP V, and poly[2-methoxy, 5-(2'-ethyl-hexyloxy)phenylene vinylene], MEH-P PV, the lowest-energy arrangement has the chains parallel, with the pe rpendicular distance between chains 3.4 Angstrom in the former case, 4 .1 Angstrom in the latter. Although there is evidence that most of the excitations created by above-band-gap light are polaron pairs or exci mers in both cases, only those in CN-PPV luminesce because the smaller interchain distance results in a much larger matrix element for emiss ion.