By Sebastian Schellhammer, Dresden Integrated Center for Applied Physics and Photonic, Technical University of Dresden

Abstract: Charge transfer (CT) excitons at donor-acceptor interfaces determine the performance of organic solar cells. The subgap absorption by such excitons is also used to design sensitive near-infrared photodetectors based on the broad CT exciton bands. However, the prediction of the energetics of the CT exciton band has ever been a great challenge. I will present an approach for an efficient computation of the CT energies at room temperature based on time-dependent density functional theory including the band tail broadening induced by thermal fluctuations in a semi-classical way. This method is demonstrated for different donor molecules with C60 as electron accepting material. A comparison to experimental CT band characteristics shows excellent agreement for both the linewidth broadening as well as the CT energies. The approach thus combines accuracy with modest computational cost. 

Hosted by Prof. Javier Rodríguez Viejo, Thermal Properties of Nanoscale Materials Leader at ICN2.