First Principles Calculations of Charge Transfer Excitations in Polymer–Fullerene Complexes: Influence of Excess Energy. (2nd October 2014)

• Record Type: Journal Article
• Authors: Niedzialek, Dorota; Duchemin, Ivan; de Queiroz, Thiago Branquinho; Osella, Silvio; Rao, Akshay; Friend, Richard; Blase, Xavier; Kümmel, Stephan; Beljonne, David
• Is Part Of: Advanced functional materials. Volume 25:Number 13(2015)
• Page Start: 1972
• Page End: 1984
• Publication Date: 2014-10-02
• Subjects: organic solar cells -- charge‐transfer excitations -- many‐body theory; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201402682
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract : The ability of quantum simulations to predict the electronic structure at donor/acceptor interfaces and correlate it with the quantum efficiency of organic solar cells remains a major challenge. The need to describe with increased accuracy electron‐electron and electron‐hole interactions, while better accounting for disorder and environmental screening in realistic interfaces, requires significant progress to improve both the accuracy and computational efficiency of available quantum simulation methods. In the present study, the results of different ab initio techniques are compared, namely time‐dependent density functional and many‐body perturbation theories, with experimental data on three different polymer/fullerene heterojunctions. It is shown that valuable information concerning the thermodynamic drive for electron‐hole dissociation or recombination into triplets can be obtained from such calculations performed on model interfaces. In particular, the ability of these approaches to reproduce the Veldman and co–workers classification of the three studied interfaces is discussed, showing the success and limits of state‐of‐the‐art ab initio techniques. Abstract : A comparative first‐principle study is presented of polymer‐fullerene complexes that differ by the excess energy for charge separation. The measured quantum efficiencies of the bulk heterojunctions can be traced back to the presence of energy‐accessible charge‐transfer states with large electron‐hole radii and molecular triplets mediating competing recombination pathways.