Energy landscapes for effective particles in conjugated polymers

The interplay between the form of an effective particle and its dynamics is explored theoretically, using singles configuration-interaction (S-CI) calculations on a polyene chain with 40 carbon atoms. The lowest-energy exciton obtained from a full S-CI calculation is compared to that obtained when the exciton is constrained to remain centered on a particular unit cell. Both the effective masses and the energy landscapes (the energy as a function of position along the chain) are in good agreement. This indicates that the dynamics have little effect on the form of the exciton itself. This decoupling of form and dynamics can be used to obtain significant computational savings. In addition, energy landscapes may be useful constructs for exploring the effects of defects and non-uniform morphology on the photophysics, as demonstrated here by examining the effects of a chain-end defect on the exciton.