How the dynamics of attachment to the substrate influence stress in metal halide perovskites
Gabriel R. McAndrews,
Boyu Guo,
Daniel A. Morales,
Aram Amassian,
Michael D. McGehee
Affiliations
Gabriel R. McAndrews
Materials Science and Engineering Program, University of Colorado Boulder, 4001 Discovery Drive, Boulder, Colorado 80303, USA
Boyu Guo
Department of Materials Science and Engineering, North Carolina State University, 911 Partners Way, Room 3002, Engineering Building I, Raleigh, North Carolina 27695, USA
Daniel A. Morales
Materials Science and Engineering Program, University of Colorado Boulder, 4001 Discovery Drive, Boulder, Colorado 80303, USA
Aram Amassian
Department of Materials Science and Engineering, North Carolina State University, 911 Partners Way, Room 3002, Engineering Building I, Raleigh, North Carolina 27695, USA
Michael D. McGehee
Materials Science and Engineering Program, University of Colorado Boulder, 4001 Discovery Drive, Boulder, Colorado 80303, USA
Metal halide perovskites have the potential to contribute to renewable energy needs as a high efficiency, low-cost alternative for photovoltaics. Initial power conversion efficiencies are superb, but improvements to the operational stability of perovskites are needed to enable extensive deployment. Mechanical stress is an important, but often misunderstood factor impacting chemical degradation and reliability during thermal cycling of perovskites. In this manuscript, we find that a commonly used equation based on the coefficient of thermal expansion (CTE) mismatch between perovskite and substrate fails to accurately predict residual stress following solution-based film formation. For example, despite similar CTEs there is a 60 MPa stress difference between narrow bandgap “SnPb perovskite” Cs0.25FA0.75Sn0.5Pb0.5I3 and “triple cation perovskite” Cs0.05MA0.16FA0.79Pb(I0.83Br0.17)3. A combination of in situ absorbance and substrate curvature measurements are used to demonstrate that partial attachment prior to the anneal can reduce residual stress and explain wide stress variations in perovskites.
