Synthetic Principles for Bandgap Control in Linear pi-Conjugated Systems.

Organic electronics are broadly anticipated to impact the development of flexible thin-film device technologies. Among these, solution-processable π-conjugated polymers and small molecules are proving particularly promising in field-effect transistors and bulk heterojunction solar cells. This Perspective analyzes some of the most exciting strategies recently suggested in the design and structural organization of π-functional materials for transistor and solar cell applications. Emphasis is placed on the interplay between molecular structure, self-assembling properties, nanoscale and mesoscale ordering, and device efficiency parameters. A critical look at the various approaches used to optimize both materials and device performance is provided to assist in the identification of new directions and further advances.

Molecular design and ordering effects in π-functional materials for transistor and solar cell applications.

For almost two decades, the search of an intrinsically-conductive organic metal has represented the major driving force for research on control of the band gap of extended π-conjugated systems. However, the emergence of the application of π-conjugated oligomers and polymers in field-effect transistors, light-emitting diodes, electrochromic devices and solar cells has introduced major changes in the chemistry of gap engineering. Besides controlled band gap, active materials for electronic and photonic applications must present appropriate absorption and/or emission properties, highest occupied and lowest unoccupied molecular orbital (HOMO and LUMO) energy levels and charge-transport properties. The aim of this short review is to present an overview of the recent trends in this area in order to identify possible directions for future research.

Molecular Engineering of the Band Gap of π-Conjugated Systems: Facing Technological Applications

This Focus Review describes the emerging class of near-infrared (NIR) organic compounds containing the conjugated polyene, polymethine, and donor-acceptor chromophores and exploration of their NIR-absorbing, NIR-fluorescence, and NIR-photosensitizing properties for potential applications in heat absorbers, solar cells, and NIR light-emitting diodes Examples of NIR organic compounds are reviewed with emphasis on the molecular design, NIR absorption, and fluorescence and particular emerging applications The donor-acceptor type of NIR chromophores are particularly introduced owing to some unique features, including the designer-made energy gaps, facile synthesis, good processability, and controllable morphology and properties in the solid state Future directions in research and development of NIR organic materials and applications are then offered from a personal perspective

Near‐Infrared Organic Compounds and Emerging Applications

Electrochemical and spectroscopic characterization of polyalkylenedioxythiophenes

Polysquaraines and polycroconaines have been synthesized. They form a new class of polymers with a small band gap, down to 0.5 eV. The small gap arises from the regular alternation of strong donor and acceptor-like moieties in a conjugated backbone.

W. ten Hoeve

Papers

A new class of small band gap organic polymer conductors