Effect of Biaxial Strain on 3D Halide Perovskites
Nicholas Rolston a
a Arizona State University, Department of Chemistry, Arizona State University, Tempe, Arizona, 85287, United States
Proceedings of Strain and 2D perovskites Seminar (S2DP)
Online, Spain, 2022 July 11th - 11th
Organizers: Loreta A. Muscarella and Rhiannon Kennard
Invited Speaker, Nicholas Rolston, presentation 002
Publication date: 13th June 2022

Organic-inorganic metal halide perovskite semiconductors have demonstrated real promise as a next-generation thin film photovoltaic technology based on unprecedented gains in device efficiencies and electronic tunability. However, the lack of device reliability remains a key drawback. We show that there are large, tensile stresses that form during perovskite processing, which is a direct consequence of the large mismatch in coefficients of thermal expansion (CTE) between stiff substrates (i.e., silicon and glass) and the perovskite. Perovskites already suffer from a number of instabilities—both chemically and thermomechanically—and the discovery of large tensile stress values in films is a property that, if ignored, could inhibit the long-term success of perovskite solar cells as an industrially relevant, commercialized technology. The stress is independent of any underlying charge transport layers and agnostic to fabrication methodology other than the temperature at which the perovskite is formed. The aim of this work was to understand how processing and operating conditions affect residual stress in perovskite films and to determine methods for controlling the amount of stress in the final film to engineer more reliable perovskite devices. We develop three simple approaches for reducing stress in perovskite films that involve the use of lower formation temperature, higher CTE substrates (i.e., PET and polycarbonate), and halide exchange—each of which is shown to improve stability. Our work also has important implications for device design and characterization. Specifically, reducing film stress is critical to enable reliable, module-scale perovskite devices that would otherwise be prone to delamination from the build-up of stresses.

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