However, the strength of electron-phonon coupling and charge transfer integral are comparable in most organic materials. This indicates a polaron transport mechanism that charge transports dressed with the lattice distortion it induced , which is neither bandlike nor hopping . Efforts have been devoted to going beyond the simple descriptions of hopping or band. Different time scales for inter-molecular vibration, intra-molecular vibration and inter-molecular charge transfer have been taken into accounts . Since intra-molecular vibration is much faster than inter-molecular charge transfer, the intra-molecular electron-phonon coupling has been treated as a mean-field via polaron transformation , through which, the dependence of Seebeck coefficient on doping level (chemical potential), electron-phonon coupling strength and temperature has been unraveled . On the other hand, inter-molecular vibration is much slower than the inter-molecular charge transfer. Thus, it can often be approximated classical mechanically through mixed quantum-classical approaches . Combining numerical calculation and theoretical analysis, transient localization theory has been developed for organic materials' charge transport , emphasizing the vital role of inter-molecular electron-phonon coupling in the charge transport of organic materials. Although these approaches provide insightful results in the regimes where the underlying assumption is valid, their accuracy remains unclear in the broad parameter regimes, especially the intermediate coupling regime which is believed to be relevant to high-performance organic materials. A general method for thermoelectric transport in organic materials is still absent. The main difficulty lies in the unavoidable many-body problem arising from comparable charge transfer integral and inter/intramolecular electron-phonon coupling, which limits the accuracy of analytic approaches and numerical methods.