Dresden 2026 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 37: Hybrid, Organic and Perovskite Optoelectronics and Photovoltaics III

CPP 37.6: Talk

Wednesday, March 11, 2026, 16:30–16:45, ZEU/LICH

Analysis of Charge Carrier Dynamics in Organic Solar Cells via Optical Impedance Spectroscopy — •Elias Waßmer, Jan Phillip Ott, Brian Hinz, Clemens Göhler, and Martijn Kemerink — IMSEAM, Heidelberg University, Germany

Understanding the complex dynamics of charge carriers in organic solar cells (OSCs) is essential to identify the mechanisms that lead to voltage, current and fill factor losses. In this work, we investigate these dynamics by combining conventional electrical impedance spectroscopy (EIS) with the newly implemented optical impedance spectroscopy (OIS). In OIS, in addition to a constant background illumination, a small alternating light signal is applied to investigate the photogenerated charge carriers under quasi-steady-state conditions. The results of both EIS and OIS of PM6:Y6 OSCs across a range of operating conditions are used to compare the two methods and allow us to track changes during device degradation. To interpret the measured impedance spectra, two established models are applied: an equivalent-circuit model, which maps the behaviour of the OSC onto a network of resistances and capacitances, and a rate-equation model that describes carrier generation, recombination and extraction through differential equations. Comparing these modelling approaches allows us to evaluate how well the charge-carrier dynamics are captured by each model and how this relates to the physical processes inside the OSCs. Our results show that the equivalent-circuit model is insufficient for describing OIS, indicating that a more physically motivated rate-equation model is needed to reproduce photogenerated carrier dynamics.

Keywords: Organic solar cells; Impedance spectroscopy