Quantitative characterization of exciton from GW plus Bethe-Salpeter calculation

摘要

We propose a method of classifying excitons into local-, Rydberg-, or charge transfer-type as a step toward enabling a data-driven material design of organic solar cells. The classification method is based on the first-principles many-body theory and improves over the conventional method based on state-by-state visualization of the one-electron wave functions. In our method, the exciton wave function is calculated within the level of the GW+ Bethe-Salpeter equation, which is used to obtain two dimensionless parameters for the automatic classification. We construct criteria for exciton classification from experiences with a model molecule, dipeptide. Then we check the validity of our method using a model beta-dipeptide which has a geometry and an excitation spectrum similar to the model dipeptide. In addition, we test the effectiveness of the method using porphyrin molecules, or P(1)TA and P(2)TA, for which the conventional method is hampered by the strong state hybridization associated with excitation. We find that our method works successfully for P(1)TA, but the analysis of P(2)TA is hindered by its centrosymmetry. Published by AIP Publishing.