Influence of Nonuniform Exciton Density on Diffusion Length Measurements via Photoluminescence Quenching

Addressing the challenge of energy efficiency in organic photovoltaics (OPVs) requires investigating exciton transport mechanisms. Exciton migration in OPVs is influenced by factors such as the morphology, temperature, absorption properties, and excitation conditions. In this context, the diffusion length (<i>L</i> _D) is a key parameter that characterizes overall transport efficiency. Spectroscopic techniques, particularly photoluminescence quenching, are commonly used for <i>L</i> _D measurements. However, in bilayer quencher setups, these measurements can be limited by assumptions about exciton behavior, potentially leading to inaccurate <i>L</i> _D estimates. In this work, we assess the magnitude of error in <i>L</i> _D measurements resulting from incorrect exciton generation assumptions. It was found that the error largely depends on the molecules' absorption characteristics. An analysis of common organic compounds suggests errors of up to 30%. The findings reveal an important limitation in commonly adopted experimental protocols that estimate the diffusion length. Moreover, assessing the error magnitude might aid in the interpretation of future experimental characterizations, furthering the understanding of exciton dynamics in practical setups.