Visualisation of charge-transfer excitations in donor-acceptor molecules using the particle-hole map: a case study

• Published in: Molecular physics Vol. 114; no. 7-8; pp. 1365 - 1373
• Main Authors: Li, Yonghui, Moghe, Dhanashree, Patil, Satish, Guha, Suchismita, Ullrich, Carsten A.
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 17.04.2016; Taylor & Francis Ltd
• Subjects: Case studies; Charge-transfer excitations; Computational efficiency; Coupling (molecular); Excitation; Mathematical analysis; Organic chemistry; organic photovoltaics; particle-hole map; Photovoltaic cells; Solar cells; Time dependence; time-dependent density-functional theory
• ISSN: 0026-8976; 1362-3028
• DOI: 10.1080/00268976.2015.1137642

Charge-transfer (CT) excitations are essential for photovoltaic phenomena in organic solar cells. Owing to the complexity of molecular geometries and orbital coupling, a detailed analysis and spatial visualisation of CT processes can be challenging. In this paper, a new detail-oriented visualisation scheme, the particle-hole map (PHM), is applied and explained for the purpose of spatial analysis of excitations in organic molecules. The PHM can be obtained from the output of a time-dependent density-functional theory calculation with negligible additional computational cost, and provides a useful physical picture for understanding the origins and destinations of electrons and holes during an excitation process. As an example, we consider intramolecular CT excitations in Diketopyrrolopyrrole-based molecules, and relate our findings to experimental results.