The state of the art in the use of conjugated polymers in electronic devices is summarised and the prospects for their further development discussed.

The methods for synthesising by precursor routes films of insoluble poly(phenylene vinylene) (PPV), the prototypical poly(arylene vinylene) (PAV) are described and compared and its properties discussed. Methods for preparing soluble substituted PPVs are described and their structure–property relationships discussed. By suitable choice of structure, PAVs with emission colours ranging from the blue to the near infra-red have been made and tested in light-emitting diodes. The choice of substituents has also been used to enhance the charge accepting and transporting properties of PAVs, thus improving their efficiency in devices. The efficiency of polymer-based LEDs is also affected by the presence of defects in the polymer structures and methods have been developed to minimise these, enabling commercially-viable LEDs to be made using PAVs. The potential use of PAVs in OTFTs and OPVs is also discussed.

The methods for synthesising polyacetylene are discussed and compared. As unsubstituted polymer is insoluble, precursor methods must be used to make films suitable for use in devices. While the fact that doped polyacetylene is conducting is of scientific interest, its instability and lack of luminescece has made it useless for practical applications. Substituted polyacetylenes can be made which are both soluble and luminescent, making them potentially useful in LEDs.The synthesis and properties of such polymers are discussed as well as their structure–property relationships and potential for use in devices.

Polythiophenes are the most widely studied class of heteroarene-based polymers. The properties of poly(3-alkylthiophene)s have been shown to depend upon the degree of regioregularity in the polymer backbone. Routes have been developed to make almost completely regioregular polymers with nearly 100% head-to-tail couplings. These regioregular polymers show much better chain packing in the solid state and significantly better charge carrier mobilities, making them suitable for use in OTFTs. They show less promise as LED materials due to low emission efficiencies, but are promising as solar cell materials. A combination of regioregular poly(3-hexylthipophene) and a fullerene acceptor is the most widely studied donor–acceptor pair in OPVs, with device efficiencies of over 5% combined with a relatively inexpensive synthesis, making it potentially commercially viable.

While LEDs are the most common emissive device, other emissive devices using conjugated polymers are possible. The use of emissive polymers in devices such as light-emitting electrochemical cells, chemiluminescence cells and light-emitting transistors is described and the different design features needed to optimise their performance discussed. The use of polymers in microcavbities and lasers is discussed. While optically-pumped lasing has been demonstrated, electrically-pumped lasing form organic materials remains to be demonstrated but is not theoretically impossible. The prospects for integrated polymers devices such as optocouplers are also discussed.

White electroluminescence is required for lighting applications. This is obtainable by either blending two materials with complementary colours (usually blue and red or orange) or by obtaining simultaneous emission from independent chromophores with complementary colours. The designs of polymers that have been used to achieve this are described and compared and examples of the best performing materials given.

Conjugated polymers are semiconductors, which if doped can become conducting. Their electronic properties make them suitable for use in organic electronic devices such as transistors (OTFTs), light-emitting diodes (OLEDs) and solar cells (OPVs). The operating principles of these devices are discussed. Each of these devices have different requirements for their active materials. Among the important parameters which must be considered to optimise device performance are the energy difference between the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO) (known as the bandgap) which controls which colours of light can be absorbed or emitted, the energy levels of the HOMO and LUMO, which control the rate at which charges can be injected and extracted and the mobility of the charge carriers within the material. These parameters must be considered in designing or selecting suitable materials for use in these devices.

Methods for preparing soluble poly(arylene ethynylene)s (PAEs) and PAE-PAV copolymers are described and compared. The structure–property relationships in such polymers are described and their potential applications in devices such as LEDs and sensors discussed.

Non-linear polymers, including hyperbranched and star polymers, and dendrimers, which contain emissive chromophores, have been made. Routes to make them are described and compared and their utility in LEDs is discussed.