Theoretical calculations of the electroabsorption spectra of perylenetetracarboxylic dianhydride

A three-dimensional analog of the Merrifield model is proposed to study excitons in solid perylenetetracarboxylic dianhydride (PTCDA). Its relevant parameters are estimated by independent calculations, and finally determined by fitting the experimental absorption and electroabsorption spectra of PTCDA films; the optimum values obtained from the fit correspond well with the calculated values. The results justify description of PTCDA excitons within a one-dimensional model, as proposed in the literature. The calculated spectra are generally in good agreement with the experimental ones, with the exception of the directional properties of the electroabsorption signal. A possible reason for this discrepancy is suggested. Generally, the results highlight the prominent role of charge-transfer excitons in the electroabsorption spectrum of PTCDA by showing the experimental features that are difficult to explain without invoking these states.