Conjugated polymers are promising materials for organic thermoelectrics because they combine low thermal conductivity, mechanical flexibility, and solution processability. Moreover, their electrical conductivity can be tuned over several orders of magnitude through molecular doping, making them suitable for thermoelectric power generation. However, the performance of n-doped conjugated polymers lags behind that of their p-doped counterparts. The primary reason for this is the difficulty in achieving high doping efficiency while maintaining the microstructure required for efficient charge transport. 

This thesis investigates the factors governing doping efficiency in n-doped conjugated polymers, focusing on solvent affinity, polymer chain-length ensemble, and side-chain chemistry. To address this issue, molecularly doped polymer films were studied using optical spectroscopy, quantitative polaron analysis, grazing-incidence wide-angle X-ray scattering (GIWAXS), electron paramagnetic resonance (EPR), and thermoelectric characterization. 

The results show that doping efficiency is not determined by the nominal doping concentration alone. Instead, it strongly depends on dopant incorporation, charge generation, and the ability of the polymer microstructure to maintain a transport-supporting pathway after doping. The solvent affinity controls the phase selectivity of the dopant in the polymer matrix. The polymer chain-length ensembles influence the charge transport pathway. The side-chain chemistry modulates host–dopant compatibility and, in catalyzed doping platforms, governs the dispersion of the catalyst within the polymer matrix and the resulting microstructure of the doped film. In these studies, higher doping efficiency and thermoelectric performance are associated with a system that generates and transports charge efficiently while minimizing disruption to the solid-state transport network. 

Overall, this thesis demonstrates that achieving high electrical conductivity and high power factor in n-doped conjugated polymers requires more than just strong dopants or high dopant loading. Effective doping must be achieved while preserving a favorable molecular microstructure that supports efficient charge transport. These findings provide practical design principles for improving doping efficiency and advancing n-type organic thermoelectric materials.