Browsing by Subject "Electronic structure methods"

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    Static and Dynamic Charge and Energy Transport in Organic Electronics
    (2018-06) Ghosh, Soumen
    Organic electronic materials are a new generation of materials that have the potential to move our society to clean and renewable energy sources, but the efficiency of these materials has only recently become competitive with that of their inorganic counterparts. One of the major challenges to increasing the efficiency of organic materials is our present inability to understand in detail the mechanisms of energy and charge transport within them. Computational modeling can play a very important role in understanding such mechanisms and discovering new materials. However, accurate modeling of charge and energy transfer processes remains challenging for many electronic structure methods. Often it is not enough to just model static properties of these systems, and charge and energy transfer dynamics need to be studied as well. Considering the large size of these systems, such modeling is still not practical with ab-initio electronic structure methods and current computational power. Herein, I report studies of the charge-transport properties of both small organic electronics and molecular wires. We have tried to understand structure-function relationships in these materials and suggest how chemical modification may affect charge-transport mechanisms. We have also tested multiconfiguration pair-density functional theory, which is a very accurate electronic structure method for recovering both static and dynamic electron correlation, for ground- and excited-state charge transfer. Finally, we have developed a new method for modeling electronic dynamics in chemical systems by combining semiempirical Hartree-Fock theory with real-time dynamics. We have used this method to calculate UV/Vis spectra of medium and large organic systems. We have developed a new approach to characterize different peaks in real-time spectra, and we have also developed a new approach for modeling exciton dynamics using real-time approaches.