Effective Enhancement of the Second‐Order Nonlinear Optical Responses of Graphynes by Introducing π‐Conjugated Chains with Donor/Acceptor Groups

Abstract

AbstractUsing density functional theory calculations, we have analyzed second‐order nonlinear optical (NLO) properties of a series of −(CH=CH)m−NH2/NO2‐modified graphynes (GY[n]) (n=1−3;m=1−6, 9, 12). This type of modification can induce evident electron transfer between the graphyne and conjugated chain and decrease the transition energy, resulting in the system exhibiting a large static first hyperpolarizability (β0). Theβ0values of the GY[n]−(CH=CH)m−NH2/NO2show a monotonously increasing trend with lengthening the −(CH=CH)m−NH2/NO2chain fromm=1 to 12. Further, the NO2‐modified system has a higherβ0value than the corresponding NH2‐modified system with the same π‐conjugated length. Compared with the single‐modified GY[1], the −(CH=CH)m−NH2/NO2co‐modified GY[1] systems exhibit better NLO responses. For GY[n]−(CH=CH)m−NO2, whenm=1−4, theβ0value increases with increasing the size of graphyne, while form=5, 6, 9, 12, the varying order is reversed. Solvent and frequency dispersion effects are also analyzed. The polarizable environment has a significant influence on hyper‐Rayleigh scattering first hyperpolarizability (βHRS).