Perovskite triple and quadruple junction solar cells

Metal halide perovskite solar cells have advanced from an intriguing scientific discovery into a viable option for future renewable energy. Record single and tandem junction perovskite solar cells already provide power efficiencies close to 26% and 30%, respectively. The aim of this project is to achieve the next target in photovoltaic energy conversion by developing perovskite triple and quadruple junction solar cells towards efficiencies of 35% to 40% using cheap solution-processable materials and affordable technologies. This is a tremendous challenge that has not been attempted. It involves designing and making new materials and device architectures that push every single step in the conversion process close to its intrinsic limits, and eliminate any electrical and optical losses close to perfection. The project will focus on solving important hurdles to reach this ambitious goal. New perovskites will be designed by compositional engineering to create thin-film materials with optical bandgaps in the range of 1.2 to 2.3 eV. Unique spectroscopic techniques will identify the nature and location of the defects, either in the bulk or at interfaces with the charge-selective contacts, that give rise to nonradiative recombination of electrons and holes and that thereby contribute a loss of open-circuit voltage, limiting the performance. By adapting deposition conditions, using passivation strategies, and synthesizing new materials for the selective collection of electrons and holes these losses are minimized to provide optimized sub-cells in the required bandgap regions. Guided by optical modeling, monolithic triple and quadruple junction solar cells will be fabricated by stacking three or four different bandgap perovskite sub-cells in series using recombination junctions designed to provide near-zero electrical and optical losses. This challenging but promising effort can result in solar cells that provide power conversion efficiencies between 35% and 40%.