posted on 2023-12-06, 19:00authored byBoyu Guo, Mihirsinh Chauhan, Nathaniel R. Woodward, Gabriel R. McAndrews, Gaurab J. Thapa, Benjamin M. Lefler, Ruipeng Li, Tonghui Wang, Kasra Darabi, Michael D. McGehee, Aram Amassian
Metal halide perovskites (MHPs) are
promising candidates
for next-generation
thin film photovoltaics and high-performance tandems. Solution-processed
MHP films are susceptible to residual stress that can induce undesirable
surface wrinkles. However, the origins and evolution of stress during
solution processing remain elusive. In this work, we utilize multimodal in situ characterizations, including substrate curvature,
reflectance, absorbance, and photoluminescence, to monitor stress
and morphology evolution during MHP film formation. A film formation
model emerges, consisting of a perovskite top crust on a semirigid
sol with the ability to transfer mechanical forces. The phase transformation
induces tension in the MHP crust, while shrinkage of the sol causes
additional compression and surface wrinkles. Wrinkle-free films are
formed through dynamically balancing forces between the crust and
the sol. This study provides a powerful toolkit for the fast-growing
area of stress engineering in MHP photovoltaics to achieve dynamic
control of film stress and surface morphology.