Abstract

A promising way to lower the lasing thresholds is to use energy transfer in host-guest systems to red-shift the emission sufficiently far from the host absorption that self-absorption by the host becomes negligible.1,2 The dipole-dipole interaction leads to efficient, long-range energy transfer from an absorbing host chromophore to an emitting guest chromophore.³ We are using poly (2,3-diphenyl-5-hexyl-1,4-phenylenevinylene) (DP6-PPV) and poly[2-(meta-2′-ethylhexoxyphenyl)-1,4-phenylenevinylene) (m-EHOP- PPV) as host polymers, and polyl2,5-bis (2'-ethylhexoxy)-l ,4-phenylenevinylene) (BEH-PPV)and poly(2,5-bis(cholestanoxy)-1,4-phenylenevinylene) (BCHA-PPV) as guest polymers. Figure 1 shows the spectral results for m-EHOP-PPV (upper graph), BEH-PPV (middle graph), and 4% of BEH-PPV in m-EHOP-PPV (lower graph). The dashed lines show the optical density while the dotted lines show the photoluminescence (PL) spectra. Positive changes in the solid lines indicate stimulated emission (SE), while negative changes indicate photoinduced absorption (PA). By blending, the emissive properties are improved substantially, the absorption of the blend resembles the absorption of the host polymer, while the PL resembles the emission from the guest (slightly red-shifted), indicating complete energy transfer.

© 1999 Optical Society of America