Electron Correlation Effects on the Photophysics and Device Physics of Pi-conjugated Polymers

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0101659MazumdarThis grant, jointly funded by the Materials Theory Program in DMR and the Theoretical and Computational Chemistry Program in CHE, supports theoretical and computational research on the fundamental science and device physics of p-conjugated polymers. The research has three foci: (1) The PI aims to develop a complete theory of excited state absorption in photoluminescent p-conjugated polymers like poly(para-phenylenvinylene) (PPV) and poly(paraphenylene) (PPP), and of acene molecular crystals. This will involve understanding the nature of two-photon states seen in ultrafast spectroscopy and their relaxation mechanisms. (2) A goal of the work is to develop a conceptual framework for designing photoluminescent p-conjugated polymers that emit in the infrared. Identification of real materials that have small optical gaps, but nevertheless, posses the excited state ordering conducive to photoluminescence is planned. (3) The PI plans to develop a general theoretical technique for calculating the relative cross-sections of competing charge-transfer reactions between molecular components of organic light emitting diodes (OLEDs) and photovoltaic devices. The aim is to reach a quantitative theory of the yields of singlet verses triplet excitations in OLEDs and to understand the material dependence of the efficiencies of photoinduced charge transfer processes. To describe the electronic states in these materials, the PI will begin from the Pariser-Parr-Pople p-electron Hamiltonian for oligomers and molecular systems and perform calculations using the multiple-reference doubles configuration interaction (MRDCI) and a diagrammatic exciton basis valance bond method developed by the PI. The MRDCI allows proper truncation of basis states, while the exciton basis gives pictorial descriptions of correlated eigenstates, which in turn lead to mechanistic descriptions of the photophysics. Calculations of the intermolecular or interchain charge transfer reactions that occur in OLEDs and photovoltaic processes will be performed within a time-dependent Schr0101659MazumdarThis grant, jointly funded by the Materials Theory Program in DMR and the Theoretical and Computational Chemistry Program in CHE, supports theoretical and computational research on the fundamental science and device physics of pi-conjugated polymers. The research has three foci: (1) The PI aims to develop a complete theory of excited state absorption in photoluminescent pi-conjugated polymers like poly(para-phenylenvinylene) (PPV) and poly(paraphenylene) (PPP), and of acene molecular crystals. This will involve understanding the nature of two-photon states seen in ultrafast spectroscopy and their relaxation mechanisms. (2) A goal of the work is to develop a conceptual framework for designing photoluminescent pi-conjugated polymers that emit in the infrared. Identification of real materials that have small optical gaps, but nevertheless, posses the excited state ordering conducive to photoluminescence is planned. (3) The PI plans to develop a general theoretical technique for calculating the relative cross-sections of competing charge-transfer reactions between molecular components of organic light emitting diodes (OLEDs) and photovoltaic devices. The aim is to reach a quantitative theory of the yields of singlet verses triplet excitations in OLEDs and to understand the material dependence of the efficiencies of photoinduced charge transfer processes. To describe the electronic states in these materials, the PI will begin from the Pariser-Parr-Pople pi-electron Hamiltonian for oligomers and molecular systems and perform calculations using the multiple-reference doubles configuration interaction (MRDCI) and a diagrammatic exciton basis valance bond method developed by the PI. The MRDCI allows proper truncation of basis states, while the exciton basis gives pictorial descriptions of correlated eigenstates, which in turn lead to mechanistic descriptions of the photophysics. Calculations of the intermolecular or interchain charge transfer reactions that occur in OLEDs and photovoltaic processes will be performed within a time-dependent Schrodinger formulation that allows the monitoring of relative yields of competing charge transfer interactions. %%%This grant, jointly funded by the Materials Theory Program in DMR and the Theoretical and Computational Chemistry Program in CHE, supports theoretical and computational research on the fundamental chemical, photophysics, and device physics of pi-conjugated polymers. The PI will study the fundamental physical processes involved in, or that interfere with, the absorption and emission of light in pi-conjugated polymers. Quantum chemical techniques together with methods developed by the PI will be used to perform quantitative calculations that include the effects of electronic correlations. The work will contribute to the search for novel photoluminescent materials that are candidates for use in infrared lasers and research on the OLEDs is expected to predict dependencies of electroluminescence efficiency on materials properties. This project will provide a graduate level and higher learning environment for training in the chemistry, physics, and optics of pi-conjugated polymers.***dinger formulation that allows the monitoring of relative yields of competing charge transfer interactions. %%%This grant, jointly funded by the Materials Theory Program in DMR and the Theoretical and Computational Chemistry Program in CHE, supports theoretical and computational research on the fundamental chemical, photophysics, and device physics of p-conjugated polymers. The PI will study the fundamental physical processes involved in, or that interfere with, the absorption and emission of light in p-conjugated polymers. Quantum chemical techniques together with methods developed by the PI will be used to perform quantitative calculations that include the effects of electronic correlations. The work will contribute to the search for novel photoluminescent materials that are candidates for use in infrared lasers and research on the OLEDs is expected to predict dependencies of electroluminescence efficiency on materials properties. This project will provide a graduate level and higher learning environment for training in the chemistry, physics, and optics of p-conjugated polymers.***