Polarisation of singlet and triplet excited states in a platinum-containing conjugated polymer
JS Wilson, RJ Wilson, RH Friend, MK Al-Suti, MRA Al-Mandhary, MS Khan, A Köhler
Phys. Rev. B., 67 (2003) 125206
We investigate the polarization of optical transitions associated with the singlet S1 and triplet T1 and Tn excited states in a uniaxially aligned platinum-containing conjugated polymer which contains a 2-methoxy-5-(´-ethyl)-hexyloxy (MEH)-substituted phenyl ring. For the singlet S1 state, which is extended along the polymer chain, we find the corresponding absorption and emission to be polarized parallel to the chain as seen for other conjugated polymers. However, for the triplet excited states, we find that the emission from the highly localized T1 state has components both parallel and perpendicular to the polymer chain, while the absorption from T1 into the delocalized Tn state is polarized entirely parallel to the chain. We discuss this connection between the spatial extent of the excited state and the polarization of the associated optical transitions and consider how the spin-orbit coupling mechanism can influence the polarization of emission from the T1 state.