Scientists at TU Dresden and Hasselt University in Belgium investigated the physical causes that limit the efficiency of novel solar cells based on organic molecular materials.
Scientists at TU Dresden and Hasselt University in Belgium investigated the physical causes that limit the efficiency of novel solar cells based on organic molecular materials. Currently, the voltage of such cells is still too low - one reason for their still relatively low efficiencies. In their study, by investigating the vibrations of the molecules in the thin films, the scientists were able to show that very fundamental quantum effects, so-called zero point vibrations, can make a significant contribution to voltage losses. The study has now been published in the journal Nature Communications.
Solar cells are a crystallization point of high hopes for the necessary transformation of the global energy production. Organic photovoltaics (OPV), which is based on organic, i.e. carbon-based materials, could be ideally suited to become an important pillar in the energy mix of the "renewables" because they have a better ecological balance sheet compared to conventional silicon-based modules and only a small amount of material is required to produce the thin films. However, a further increase in efficiency is necessary. It is based on various characteristic values such as the open-circuit voltage, whose too low values are currently a main reason for still quite moderate efficiencies of OPV.
The study investigated physical reasons for this - including the vibrations of the molecules in the thin films. It was shown that the so-called zero point vibrations - an effect of quantum physics that characterizes the motion at absolute temperature zero - can have a significant influence on voltage losses. A direct relationship between molecular properties and macroscopic device properties was demonstrated. The results provide important information for the further development and improvement of novel organic materials.
Read more at Technische Universität Dresden
Illustration of the generation of charge pairs (excitons), the precursors of free charge carriers in the active layer of an organic solar cell. Free charge carriers then generate an electric voltage at the contacts of the cell. The lower image section shows a microscopic model of the organic thin film. CREDIT: M. Panhans
