Optimum Exchange for Calculation of Excitation Energies and Hyperpolarizabilities of Organic Electro-optic Chromophores

Citations Over TimeTop 10% of 2014 papers

Abstract

Organic electro-optic (OEO) materials integrated into silicon-organic hybrid devices afford significant improvements in size, weight, power, and bandwidth performance of integrated electronic/photonic systems critical for current and next generation telecommunication, computer, sensor, transportation, and defense technologies. Improvement in molecular first hyperpolarizability (β), and in turn electro-optic activity, is crucial to optimizing device performance. Common hybrid density functional theory (DFT) methods, while attractive due to their computational scaling, often perform poorly for optical properties in systems with substantial intramolecular charge-transfer character, such as OEO chromophores. This study evaluates the utility of the long-range corrected (LC) DFT methods for computation of the molecular second-order nonlinear optical response. We compare calculated results for a 14-molecule benchmark set of OEO chromophores with the corresponding experimentally measured β and one-photon absorption energy, λmax. We analyze the distance dependence of the fraction of exact exchange in LC-DFT methods for accurately computing these properties for OEO chromophores. We also examine systematic tuning of the range-separation parameter to enforce Koopmans'/ionization potential theorem. This tuning method improves prediction of excitation energies but is not reliable for predicting the hyperpolarizabilities of larger chromophores since the tuning parameter value can be too small, leading to instabilities in the computation of βHRS. Additionally, we find that the size dependence of the optimal tuning parameter for the ionization potential has the opposite size dependence of optimal tuning parameter for best agreement with the experimental λmax, suggesting the tuning for the ionization potential is unreliable for extended conjugated systems.

Related Papers

• → Effect of modified donor units on molecular hyperpolarizability of thienyl-vinylene nonlinear optical chromophores(2010)54 cited
• → Environmental and Excitonic Effects on the First Hyperpolarizability of Polar Molecules and Related Dimers(2008)25 cited
• → Unraveling Excitonic Effects for the First Hyperpolarizabilities of Chromophore Aggregates(2019)13 cited
• → Theoretical predictions of nonlinear optical characteristics of Y-type chromophores with quinoxaline moieties in a bridge(2021)3 cited
• Unraveling Excitonic Effects for the First Hyperpolarizabilities of Chromophore Aggregates(2019)