Γ-Graphyne: A Promising Electron Acceptor for Organic Photovoltaics

Abstract

The most significant discovery of recent years is graphene, which consists of a single layer of sp2-hybrid carbon atoms arranged in a two-dimensional (2D) honeycomb lattice nanostructure.Graphynes – a two-dimensional materials similar to graphene, but composed of sp-hybridized carbons periodically integrated into a sp2-hybridized carbon network. Structure of graphynes were first theoretically proposed in 1987 by Baughman et al.[1] More than 20 years later, in 2010, Li et al. developed the first successful methodology for creating γ-graphdiyne films [2]. Despite the significant attention from the scientific community, only recently Hu et al. reported the synthesis of γ -graphyne with unified long-range crystalline structure [3].We demonstrate that γ -graphyne is an efficient electron acceptor due to its low LUMO and its ability to delocalize an excess charge. Moreover, in contrast to other 2D sheets like graphene its electronic properties are not sensitive to vacancy defects. Investigation of photoinduced electron transfer processes in complexes of γ -graphyne with typical electron-accepting and electron-donating partners shows that the lowest excited states with donors are charge separated states formed by the electron transfer from partner to γ -graphyne. This electron transfer is thermodynamically favorable and occurs on nano-to-picosecond time scale. In contrast, electron transfer from γ -graphyne to strong electron acceptors such as fullerenes or arylenediimides is unlikely [4].