The broader impact/commercial potential of this Small Business Innovation Research (SBIR) Phase I project is an opportunity to open up new applications that depend on mobile power and dramatically lower the cost of residential, commercial, and utility-scale solar power. The project will develop lightweight, flexible, and extremely efficient photovoltaic (PV) modules using perovskite absorbers. Double-junction or tandem solar cells can reach far higher power conversion efficiencies than traditional single-junction cells (45% vs. 32%) by using two absorbing layers that absorb complementary parts of the solar spectrum; however, tandem cells have previously been too expensive for mainstream applications. This project uses perovskite materials to make tandem solar cells on flexible substrates at a lower cost than conventional cells by using high-throughput manufacturing and lower-cost materials. These efficient, lightweight, and flexible modules will open the door to long-endurance unmanned aerial vehicles, supplemental charging for electric cars, solar power for commercial buildings with roofs too weak for typical panels, and lower installation, module, and total system costs for residential, commercial, and utility-scale solar plants. The proposed project addresses the technical challenges associated with making flexible perovskite tandem solar cells efficient, stable, and low cost. Perovskite tandem solar cells have been demonstrated previously, but never in a lightweight and flexible format. Such a format creates unique technical challenges associated with delamination of the many layers in the tandem device stack, and further requires every layer to be robust to fracture. A critical area of work for flexible perovskite tandem solar cells is in developing robust, flexible, and dense diffusion barrier layers that can both conduct current and block the migration of ionic species between various layers. Much of the proposed work focuses on optimizing these barrier layers to prevent various degradation modes, some general to all perovskite solar cells and some unique to perovskite tandem solar cells. Other key focus areas include developing a flexible device architecture with improved adhesion between layers and a flexible encapsulation strategy. Realizing these goals will pave the way for highly efficient and flexible solar cells at substantially lower costs than today?s leading solar 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.
