Concentration-dependent intra- and inter-chain charge transfer dynamics of conjugated polymers explored by transient absorption spectroscopy

Conjugated polymers exhibit significant application potential in the field of organic optoelectronic devices owing to their unique photophysical properties. Poly(2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylene vinylene) (MDMO-PPV) presented a distinct photoluminescence (PL) emission at the different concentration. The two PL components of intra- and inter-chain emissions at 556 nm and 592 nm can be adjusted. Ground state bleaching and stimulated emission features were observed below and after 524 nm in the transient absorption spectrum of the low MDMO-PPV concentration. As the concentration increased, the ground state bleaching feature red-shifted, indicating a reduction of the band gap. At high concentrations, intra-chain charge transfer was substituted by the inter-chain charge transfer. The lifetime of inter-chain emission turned increased due to the charge aggregation.