Kell Fremouw

Kell Fremouw completed his B.S. in Engineering Physics at the University of Maine in 2023. He joined the McGehee research group at the University of Colorado Boulder in the summer of 2023. Kell studies how perovskite solar cells degrade under reverse bias conditions. Outside of research he enjoys kayaking, skiing, disc golf, and hiking with his dog.

Graduate Advisor: Mike McGehee (University of Colorado Boulder)
IRES-Perovskites Host: Emil List-Kratochvil (Humboldt Universität Berlin)

Uncovering the Effect of Mobile Ions on Degradation in Perovskite Solar Cells Under Reverse Bias

Perovskite solar cells (PSCs) pass current and degrade quickly in reverse bias, limiting their operational stability. However, simple band diagrams indicate that PSCs should not pass current in reverse bias. Asymmetry in the mobile ion distribution has been hypothesized to cause steep band bending and allow a tunneling current to flow, but typical reported mobile ion concentrations of ~10¹⁷ ions/cm³ are too small to explain the strong observed current. Here, we explore the distribution of mobile ions and dopants in PSCs throughout reverse bias and recovery. Changes in the amount and distribution of mobile ions and dopants are linked to loss in PCE during reverse bias, and restoration of PCE during recovery in forward bias.

IRES 2025 Final Report