Temperature-Dependent Charge-Transfer-State Absorption and Emission Reveal the Dominant Role of Dynamic Disorder in Organic Solar Cells

In organic photovoltaics, the energetic characteristics of the charge-transfer state determine the device properties, and are defined by molecular interactions at the donor-acceptor interface. This study uses sensitive spectroscopy to investigate the roles of morphological disorder and molecular dynamics in charge-transfer states, which ultimately affect the open-circuit voltage. The authors model temperature-dependent data and find that dynamic, rather than static, disorder determines the optical properties of the charge-transfer states. Thus, to develop highly efficient organic solar cells, the intramolecular properties of the working materials should receive more attention.