Toward Understanding the Built-in Field in Perovskite Solar Cellsthrough Layer-by-Layer Surface Photovoltage Measurements
Gutierrez-Partida, E., Rusu, M., Zu, F., Raoufi, M., Diekmann, J., Tokmoldin, N., Warby, J., Menzel, D., Lang, F., Shah, S., Shoaee, S., Korte, L., Unold, T., Koch, N., Kirchartz, T., & Neher, D., Stolterfoht, M. (2025). ACS Applied Materials & Interfaces, 17(7), Article 7. https://doi.org/10.1021/acsami.3c22286
The goal of this study was to understand the origin and distribution of the built-in voltage (VBI) in perovskite solar cells (PSCs) by performing layer-by-layer surface photovoltage (SPV) measurements across different device stacks.
Key findings revealed that the SPV gradually increases with each added layer but that the most significant contribution to the VBI stems from the top metal electrode (e.g., Cu), rather than the transport layers. This suggests that the VBI in pin-type PSCs largely originates from the work function difference between the electrodes. Numerical simulations confirmed that partial device stacks could exhibit large quasi-Fermi level splittings (QFLS) without significant internal electric fields, but achieving high open-circuit voltages (VOC) still requires a strong overall VBI.
Fluxim’s Setfos software was used for numerical drift-diffusion simulations including the influence of mobile ions, helping to reproduce and validate the experimentally observed SPV and QFLS trends across different device configurations. Setfos enabled precise modeling of the internal fields, showcasing its critical role in understanding complex optoelectronic behaviors in PSCs.
The findings are important for the scientific community as they provide a clearer experimental and theoretical framework for how internal fields form in perovskite devices, aiding the design of more efficient and stable solar cells.