Time-resolved Forster energy transfer in polymer blends

Sub-picosecond spectroscopy and pump-probe experiments show Forster energy transfer in blends from larger gap (blue or green-emitting) host polymers p oly(2,3-diphenyl-5-hexyl-1,4-phenylenevinylene) (DP6-PPV) or poly[2-(meta-2 '-ethylhexoxyphenyl)-1,4-phenylenevinylene) (m-EHOP-PPV) to the smaller gap , red-emitting guest polymer poly(2,5-bis(2'-ethylhexoxy)-1,4-phenyleneviny lene) (BEH-PPV). The dynamics of the stimulated emission (SE) and photoindu ced absorption (PA) of the blends indicate that 10-20 ps are required for c omplete energy transfer. Quantitative measurements of energy transfer rates give a Forster interaction range of 3-4 nm, 1.4 times longer than the theo retical values as calculated from the spectral overlap. We attribute this d ifference to delocalization of the excited state. Insufficient spectral ove rlap between the emission of the host and absorption of the guest is shown to be the cause for the absence of energy transfer in a blend with poly(2,5 -bis(cholestanoxy)-1,4-phenylenevinylene) (BCHA-PPV) as the guest polymer. (C) 1999 Elsevier Science S.A. All rights reserved.