Grant: Alliance Grants

This proposal outlines an interdisciplinary plan to expand the boundaries of solar-energy capture and conversion through the synthesis of carbon-rich molecules and materials. Strategically designed organic molecules will be used to overcome the thermodynamic limitations inherent to the current generation of processes used to convert light into electricity. Specifically, molecular design can be used to answer both fundamental and applied questions regarding two processes, singlet fission (SF) and triple-triplet annihilation upconversion (TTA-UC). The combination of these two processes in organic materials offers the potential for improved efficiency in next generation devices to harness solar energy. We propose that the stepwise substitution of acenes will allow incorporation of groups that can provide stability, solubility, and function (acenes = molecules featuring a linearly fused sequence of benzene rings). Precise control of the structure of acenes will facilitate solar-energy conversion through SF and TTA-UC. Careful molecular design is then combined with world-leading theoretical and photophysical characterization to optimize the efficiency of organic molecules for next generation solar cells. Photophysical analyses will provide a detailed mechanistic understanding of SF and TTA-UC through femto-, pico-, nano-, and micro-second-resolved experiments. In other words, we use spectroscopy to "watch" molecules over time frames as fast as one quadrillionth of a second to as slow as one thousandth of a second. To understand fundamental aspects of SF and TTA-UC, we will rely on complex theoretical and computational methods. These simulations provide theoretically derived models of these ultrafast processes that are spectroscopically observed after the molecules absorb light. Coupled with experimental measurements, a wholistic picture is developed both to understand individual classes of molecules as well as plan for their implementation into solar conversion schemes.