Thermoelectric Energy Conversion in Molecular Junctions Out of Equilibrium

Understanding time-resolved quantum transport is crucial for developing next-generation quantum technologies, particularly in nano- and molecular junctions subjected to time-dependent perturbations. Traditional steady-state approaches to quantum transport are not designed to capture the transient dynamics necessary for controlling electronic behavior at ultrafast timescales. In this work, we present a nonequilibrium Green’s function formalism, within the recently developed iterated generalized Kadanoff-Baym ansatz (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>i</a:mi><a:mi>GKBA</a:mi></a:math>), to study thermoelectric quantum transport beyond the wide-band limit approximation (WBLA). We employ the Meir-Wingreen formula for both charge and energy currents and analyze the transition from Lorentzian line-width functions to the WBLA, identifying unphysical divergences in the latter. Our results highlight the importance of finite-bandwidth effects and demonstrate the efficiency of the <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>i</c:mi><c:mi>GKBA</c:mi></c:math> approach in modeling time-resolved thermoelectric transport, also providing benchmark comparisons against the full Kadanoff-Baym theory. We exemplify the developed theory in the calculation of time-resolved thermopower and thermoelectric energy conversion efficiency in a cyclobutadiene molecular junction.