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TYC@Imperial:Understanding optical absorption in organic semiconductors

Alise Virbule

Department of Physics

Monday 18th June 2018
Time: 12.00pm
Venue: Lecture Room G20, Royal School of Mines, Imperial College London
Contact: Ms Hafiza Bibi
Tel: 02075947252

Abstract: Organic semiconductors have shown great promise as candidate materials for solar cells, whose efficiency depend on many properties, including the absorption strength within the visible spectrum. Recent studies suggest that the molecular organisation in a polymer film can have a great effect on the absorption strength without changing the material’s chemical composition. Widely used electronic structure methods such as time-dependent density functional theory cannot access the length scales necessary to study the effect of polymer conformation on the optical properties, so instead coarse-grained methods need to be employed. In this work I am using an extended Hubbard Hamiltonian parameterised from first principles calculations to calculate the optical properties of different types of oligomers and study how their absorption strength depends on chain length. The long-term goal of this project is predicting spatially averaged optical properties of a material using the knowledge of the excited states on an atomic scale and a given molecular organisation, as the understanding of the macroscopic absorption properties of known compounds can be used to aid the design of new organic materials exhibiting high optical absorption.

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