Energy harvesting at the nanoscale: From principles to functions

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The objectives of our program is to build models, develop theoretical methodologies and computational implementations, suggest new functions, and optimize performance of energy conversion systems operating at the nanoscale. Transducers of interest are photovoltaic cells, thermoelectric junctions, and heat engines such as heat pumps and refrigerators, made from physical-chemical components such as single molecules, quantum dots, thin films, organic hetero-junctions. Using simple models, our plan is to focus on the dynamics of charge and energy carriers in these systems, and interrogate the role of quantum effects on transfer rates, loss processes, fluctuations, currents, and power output and efficiency. A central aspect of systems of interest is that the dynamics of participating particles, thus the resulting operation, is strongly affected by the interaction between electronic and nonelectronic degrees of freedom, the latter comprising nuclear motion of molecules, radiation fields, and other collective excitations. Another nontrivial aspect of our work is that it inherently departs from the setting of traditional thermodynamics since quantum effects and strong interactions between the operating system and its thermal environment may govern the dynamics. Our program will constitute three interrelated parts: (i) Method development: We will advance various original theoretical and computational methodologies, numerically exact path integral methods, approximate approaches, and phenomenological treatments, to describe quantum dynamics of interacting systems in complex environments. We will specifically adapt these techniques to study charge, energy and spin transfer processes in representative models for molecular-based machines. (ii) Quantum thermodynamics: We will probe the emergence of macroscopic thermodynamics from quantum principles by studying minimal designs of quantum heat engines. (iii) Energy harvesting systems: Using the developed models, definitions, and theoretical and computational tools, we will simulate energy conversion processes in particular-factual nano-systems. Specifically, we will study thermoelectric and photovoltaic systems, and probe concepts of promise for an improved operation. Our work will contribute fundamental and practical insights over charge and energy transfer processes in molecular systems, components of electronic and thermal devices. As well, developed methods could be applied to describe processes at the core of chemical reactivity in solution and decoherence effects in quantum information technologies. The proposed research program will contribute to the advancement of knowledge, with the development of first-principle approaches for treating quantum many-body effects in complex systems, and to emerging technologies, by suggesting novel designs for nanoscale energy conversion systems.