SOLAR: Programming the Self-Assembly of Matter for Solar Energy Conversion

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The grand challenge in efficiently harvesting and converting solar radiation into electricity lies in engineering materials on multiple length scales with architectures that direct the flow of energy and the transfer and transport of charge, as in naturally occurring light harvesting systems. Organic-inorganic hybrids, prepared from functional, electro-active organic and nanostructured inorganic materials, combine desirable and tunable chemical and physical properties of the constituent organic and inorganic building blocks in a single composite, making them promising systems for solar technologies. Hybrid materials incorporate the low-cost, large-area processing and high absorbance and quantum efficiencies of organic materials with the adjustable optical properties, high carrier conductivities, and good photostability of inorganic nanostructures. Solar photovoltaic and luminescent solar concentrator technologies will be dramatically advanced if the organic and inorganic building blocks of hybrid structures can be positioned and oriented on the nanometer scale to regulate the competitive processes of charge transfer and transport, emission, and energy transfer. Hybrid organic-inorganic materials promise one of the best architectures for ultra-low-cost photovoltaic devices. Currently, the efficiency of hybrid photovoltaic devices is limited by the availability of red-absorbing, high-mobility organic and inorganic components (to match the solar spectrum and efficiently collect charge) and of composites with structures that achieve high surface area junctions, yet form well-connected organic and inorganic pathways. This project aims to produce significantly improved hybrid structures for photovoltaics. Improved hybrid materials may also enable creation of high-efficiency luminescent solar concentrators, which currently are limited in performance by materials challenges; organic and inorganic materials alone have not been found to satisfy the broad-spectrum collection, near-unity photoluminescence efficiency, low re-absorption, and good photostability required. This project brings together advances in chemical synthesis, mathematical modeling, and self-organization to control the position and orientation of organic and inorganic building blocks, exploiting advances at the frontier of chemistry, materials science, and mathematics. We will combine precisely controlled 1) molecular and supramolecular dendrimeric systems tailored to assemble with different structural motifs and 2) nanocrystals of tunable size, shape, and composition that self-assemble into single and multi-component superlattices. Structural, optical, and electrical probes will be combined with mathematical modeling of the effects of interface geometry to optimize charge transfer and transport, emission, and energy transfer. The results will enable engineering of organic-inorganic materials that will be integrated in photovoltaic devices and luminescent solar concentrators.More broadly, the research program will develop new synthetic methods and mathematical formalisms for the self-assembly of hybrid materials with tailored architectures that is important to provide materials with superior structural, electronic, and optical properties. These materials have applications in imaging, therapeutics, and information technology, in addition to energy harvesting. The project's emphasis on mathematical techniques for engineered self-assembling systems offers the potential for impact in robotics and biological systems. The project will also electronically and optically probe and establish mathematical models of the behavior of organic-inorganic heterojunctions key to their application in a range of electronic and optical devices.