Using a mesoscopic modelling approach, the authors performed computer experiments to study the influence of polymer density on bipolar charge evolution through thin layers of polydiacetylene (PDA) exhibiting specific microstructures. We found that the competition between charge transport, trapping and recombination within the polymer layer leads to several general trends, some of them being non-intuitive, as one varies polymer density. Our results show that polymer density mainly affects current and recombination efficiencies in the absence of defects or impurity states. The overall trends depend both on chain orientation relative to the electrodes and on the strength of the external applied electric field. These results suggest that adequate modelling of charge transport in electronic and optoelectronic devices based on conducting and semiconducting polymers, such as PDA, must include their structure and related key factors at mesoscopic scale. Such models provide the necessary knowledge-base to optimize the polymer film structure for electronic applications.