Modeling emission from birefringent polymer films

Summary form only given.With the increasing use of polymers in light emitting devices it is important to understand in detail how the pattern of the emitted radiation depends on the orientation of the polymer chains. The long chain molecular structure of typical polymer materials, together with the spin coating technique by which thin layers are fabricated, results in the molecules being predominantly oriented in the plane of the film. This results in significant optical birefringence. We use a classical model that accounts for spontaneous emission from within such birefringent materials in planar multilayer structures. We compare the results obtained using this model with experimental data on the radiation pattern produced by a thin film of the conjugated polymer poly[2-methoxy, 5-(2'-ethyl-hexyloxy) 1,4 phenylenevinylene] (MEH-PPV). We show that departures from the expected Lambertian radiation pattern for the MEH-PPV can be attributed to a combination of birefringence, and the dipole moment of the polymer lying in the plane of the film.