Comment on "Triplet-to-Singlet Exciton Formation in poly(p-phenylene-vinylene) Light-Emitting Diodes"

The low-lying singlet and triplet spectrum in conjugated polymers clearly show that the mechanism proposed by Lin et al. to explain their electric field dependence of singlet to triplet yield ratios is wrong. This comment, from theoretical spectrum obtained for long polyenes, shows that the phonon bottleneck proposed by Lin et al. for triplets in polyenes cannot exist.