S. Zh. Karazhanov, Institute for Energy Technology, Kjeller, Norway and Institute of Solid State Physics, University of Latvia, Riga, LatviaYttrium oxyhydride (YH3-2xO>x, YHO) belongs to the emerging class of mixed anion systems—materials incorporating multiple anion species, potentially enabling unique properties not found in single-anion counterparts. First discovered in 2011, YHO is synthesized via reactive magnetron sputtering to deposit YH, followed by oxidation in air. It exhibits photochromic behaviour under ambient conditions, transitioning from a transparent state (transmittance T > 85%) to a dark state (T ≈ 20%) upon exposure to sunlight, with nearly uniform absorption across all wavelengths.
YHO has strong potential for various technological applications, including smart windows, protective eyewear, helmet visors, and automotive roof glass. The commercialization of roll-to-roll deposited photochromic YHO has already begun through the SME Sunphade Today, the study of YHO and other rare-earth metal oxyhydrides is an increasingly attractive research field.
This talk will highlight key research findings on YHO, focusing on its physical and optical properties, including photochromic behavior under visible and ultraviolet light exposure, tunable transparency, and high optical stability with minimal degradation over multiple cycles. The temperature-dependent dynamics of YHO's transition between transparent and opaque states will also be discussed. Additionally, the presentation will cover ongoing studies related to durability and chemical stability, ensuring long-term reliability in practical applications, as well as efforts to enhance response times, cycling stability, and energy efficiency for large-scale implementation.
Theoretical advancements will be explored, including predictions of crystal structures for oxidized yttrium hydride, hydrogen-induced band structure modifications that explain its distinctive optical effects, and phenomena such as light-induced lattice breathing and lattice contraction/expansion. Furthermore, deposition techniques for small- and large-area glass and flexible substrates, prototype development, and functionality assessments in both laboratory and outdoor environments will be presented, along with insights from roll-to-roll deposition studies.