The complexity of Classical Marcus analysis for charge transfer state in organic photovoltaics

Abstract

Classical Marcus theory is widely used in organic photovoltaics (OPVs) to extract charge transfer (CT) state properties from electroluminescence (EL) and sensitive external quantum efficiency (s-EQE) spectra. However, practical donor-acceptor blends often exhibit complications such as overlap between CT and localized exciton (LE) emissions, large static energetic disorder, and weak CT oscillator strengths, all of which can limit the accuracy of simple Marcus analysis. This article discusses those issues in detail and provides a practical guide to Marcus-based CT analysis for complex cases with invisible CT states and large static disorder. An open-source Python package is released to enable semi-automated Classical Marcus analysis when CT is clearly visible.