Organic materials steadily break into the market of electronic devices (see organic electronics) as cost effective solution. Ease of production and recycling, environment-friendly chemistry, advanced molecular engineering, light weight and flexibility are additional advantages of organic electronics over inorganic. The electronic properties of these materials are determined by the π-conjugated system (see conductive polymer).
One of the challenges of computer-aided design of new materials is prediction of their structure. For organic semiconductors, due to their pronounced polymorphism and complex multiscale bulk structure, it is notoriously tough problem.
Atomic-scale resolution is often hard to achieve experimentally for molecular systems due to complex potential energy surface with multiple minima. In this case accurate first-principle modeling is the only way to refine the molecular structure.
One of the most promising applications of organic semiconductors is in photovoltaics with the best power conversion efficiencies exceeding 16%. A low-cost implementation of organic solar cells is based on bulk-heterojunction of π-conjugated molecular donor and fullerene-based acceptor: the solar radiation is absorbed by the first component resulting in the creation of an exciton migrating to the interface where the exciton is split into the hole and electron transported to the electrodes by the donor and acceptor respectively. The complex multiscale morphology of this device limits the ability of experimental approaches to pinpoint the power conversion losses and thus to avoid the blind search of highly efficient devices. In this situation a theoretical study becomes an essential complementary tool of investigation.
Field effect transistors is another major application of organic semiconductors, showing best charge carrier mobilities exceeding 10 cm2/Vs combined with high on-off ratio. The main theoretical challenge is to accurately predict the mobilities and understand mechanisms of charge transport.
Rational design of new materials relies on knowledge of structure-property relationships. Computational approach provides in-depth information about intrinsic structure and properties of materials not accessible for direct experimental studies.