Improving Efficiency and Stability of Perovskite Tandem Photovoltaics
Author: Caleb Clifford Boyd
Publisher:
Published: 2020
Total Pages:
ISBN-13:
DOWNLOAD EBOOKOrganic-inorganic metal halide perovskites are a class of semiconductor materials with excellent optoelectronic properties that hold promise for applications including photovoltaics, light-emitting diodes, and detectors. They are fabricated from low-cost, scalable solution processing or vapor deposition methods and have readily tunable optoelectronic properties through manipulation of chemical composition. This unique combination of materials properties has opened the door for low-cost tandem photovoltaics, in which a wide band gap perovskite solar cell is paired with a low band gap solar cell such as silicon, copper indium gallium diselenide, or low band gap perovskites, reducing thermalization losses that are intrinsic to single junction solar cells and enabling higher power conversion efficiencies. However, to enable commercialization of this new technology, the stability of metal halide perovskites must be improved. In this dissertation, I first describe the current understanding of degradation mechanisms for metal halide perovskite solar cells and methods to prevent them. I then discuss in detail metal oxide barrier layer design to prevent oxygen and moisture ingress and reactions between halogen species from the perovskite film and metal contacts and use these barrier layers to demonstrate efficient devices that have state-of-the-art operational and thermal stabilities. I then apply these learnings to highly efficient perovskite/silicon tandems, enabled by a stable device architecture and a novel, triple-halide (I, Br, Cl) perovskite with excellent photostability and optoelectronic properties enabled by the addition of chlorine into the lattice. I conclude with an in-depth study of interfacial reactions between the perovskite and nickel oxide, a highly desirable hole transport layer for efficient and stable perovskite tandem solar cells and demonstrate a method to prevent these reactions, improving device voltages and efficiencies.