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Abstract

Understanding charge transport in disordered materials like organic semiconductors (OSCs) and quantum dot (QD) solids is crucial for optimizing device applications. Although governed by the common physics of hopping transport, the origins of disorder differ significantly between these systems. This thesis explores the consequences of this shared physics under both equilibrium and non- equilibrium conditions. At equilibrium, distinct transport mechanisms are demonstrated: In ZnO QDs, temperature-dependent conductivity is dictated by the size-dependent charging energy distribution, while in highly doped OSCs, extreme density of state filling induces a hard-Coulomb gap, leading to the novel phenomenon of Seebeck coefficient inversion. Under high electric fields, both systems exhibit non-equilibrium "hot" carrier effects, which are described using an effective electronic temperature framework. A physically grounded heat balance model is employed to extract an effective localization length (α_eff) from field-dependent conductivity, proving the potential of α_eff as a sensitive probe of morphology in both material classes. The central contribution is the direct experimental validation of the effective temperature concept by combining direct Seebeck-based thermometry with conventional conductivity scaling in ZnO QD solids. It is then proven that the effective temperature corresponds to the real, physical temperature of the non-equilibrium carrier distribution. This confirmation establishes the effective temperature framework as a reliable tool for studying non-equilibrium phenomena in disordered systems. Finally, the research connects fundamental understanding to material processing, demonstrating how techniques like dip-coating can modify local microstructure to enhance the thermoelectric performance of OSCs.