STTR Phase I: Development of a Transparent, Near-Ultraviolet Photovoltaic Power Source for Wireless Operation of Smart Windows and IoT Devices

The broader impact/commercial potential of this Small Business Technology Transfer (STTR) Phase I project is a transparent photovoltaic technology that converts near-ultraviolet (NUV) light into point-of-use power for dynamic 'smart' windows. Energy use in buildings represents roughly 40% of total U.S. energy demand. It is projected that over half the buildings that will be in use in 2050 are already built. Retrofitting existing buildings with smart windows that regulate/monitor sunlight transmission could reduce building energy consumption by 10 - 40% and represents a $64B total addressable market, but is presently prohibitively complex and labor intensive. Transparent, NUV solar cells will simplify smart glass/film adoption by obviating the need for external wiring, thereby catalyzing deployment of smart window technologies in existing buildings to increase energy efficiency and enhance occupant health and productivity. Similarly, IoT smart devices/sensors promise to make the built environment more efficient by giving users more control over appliances, information, and energy use. Transparent NUV solar cells can provide point-of-use power to in-window IoT devices/sensors without altering aesthetics. For the photovoltaic community, the operation physics and performance of the NUV photovoltaic technology developed through this program will be of broader interest, as NUV wavelengths are inefficiently harvested by conventional photovoltaics. The proposed project will explore a photovoltaic technology that selectively absorbs near-ultraviolet (NUV) light - energy that is otherwise wasted - and efficiently converts it into high-voltage power. Solar cells harvesting NUV photons could satisfy the unmet need of powering smart windows monolithically without competing for visible or near-infrared photons that the windows seek to regulate or imposing design constraints on window aesthetics. First-generation NUV solar cells exhibit power scalability with area, and single-junction photovoltages exceeding 1.6 V (record for thin-film PV). This Phase I project aims to (1) translate NUV solar technology from rigid glass to a flexible substrate, and (2) demonstrate use of low-cost transparent electrode alternatives. These breakthroughs will allow for facile integration of NUV solar cells with smart windows for self-powered operation and intelligent management of the solar spectrum, with NUV photons powering the regulation of visible and near-infrared photons for natural lighting and heating purposes, respectively. Additionally, the aesthetically-discreet nature of flexible, transparent NUV solar cells can enable remotely-powered internet-of-things (IoT) smart devices/sensors. Accordingly, funding for this Phase I project will produce a flexible, transparent NUV solar cell prototype for field-testing with smart window and IoT device technologies. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.