This Small Business Innovation Research Program (SBIR) Phase I project explores a transformational visibly transparent photovoltaic (PV) device. Building-integrated photovoltaics (BIPV) are a promising energy pathway to capturing large areas of solar energy and increasing U.S. building efficiency at the point of utilization. However, the widespread adoption of such technologies is severely hampered by the cost and aesthetics associated with mounting traditional PV modules on siding and windows. Here, these challenges are overcome by exploiting the excitonic character of molecular and organic semiconductors that lead to "oscillator bunching" to produce PV architectures with selective absorption, i.e. exhibiting visible minima and ultra-violet (UV) and near-infrared (NIR) maxima, uniquely distinct from the band-absorption of traditional inorganic semiconductors. By using excitonic molecular semiconductors with structured absorption in the NIR/UV these devices are simultaneously optimized for high power conversion efficiency, visible light transmission, and color rendering index. Accordingly, the aim of this program is to reach relevant size, lifetime, aesthetic, and form-factor objectives that will demonstrate the feasibility of developing the proof-of-concept prototypes into a commercially viable, transparent, PV window film that can be applied to glass surfaces at the point of window fabrication or as a retrofit on existing windows. The broader impact/commercial potential of this project enables unprecedented freedom for architectural PV adoption by maintaining the aesthetics of existing building materials and the quality of natural indoor lighting: (1) increasing building efficiency and energy independence by producing electricity at the point of utilization, (2) reducing building cooling demands by rejecting infrared solar heat, supplementing or replacing existing low-E and solar-control window coatings, and (3) achieving low levelized energy costs by piggybacking on the installation, framing, and maintenance of the existing building envelope. Installed window surface area in the U.S. equipped with such films represents hundreds of terawatt-hours of potential energy, comprising energy generation and energy savings. Moreover, this project will result in a core knowledge from which future generations of transparent photovoltaic devices and materials will be designed. Visibly transparent PVs are also amenable to seamless energy harvesting within non-window surfaces such as electronic displays and mobile electronic accessories, enhancing the functionality of those products without impacting aesthetics or functionality. The deployment of transparent PVs, both domestically and abroad, supports American efforts to maintain technological and economic leadership in developing and implementing advanced technologies, by revolutionizing the way electricity is generated and consumed
