E.E. Havinga

Alternate donor-acceptor small-band-gap semiconducting polymers; Polysquaraines and polycroconaines

Abstract The idea that conjugated polymers with alternate donor and acceptor moieties in the main chain are characterized by a small band gap is proposed and explained. Experimental verification of this idea is reported in new classes of conjugated polymer semiconductors, polysquaraines and polycroconaines. These new materials show band gaps down to 0.5 eV, conductivities around 10−5 S/cm and are stable in air up 250°C or higher.

A new class of small band gap organic polymer conductors

SummaryPolysquaraines 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.

A universal relation between conductivity and field-effect mobility in doped amorphous organic semiconductors

Abstract We have fabricated metal-insulator-semiconductor field-effect transistors (MISFETs) from tetracyanoquinodimethane (TCNQ) doped with tetrathiofulvalene (TTF) and poly(β′-dodecyloxy(-α,α′−α′,α″-)terthienyl) (polyDOT3) doped with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). Experimentally we find that the measured field-effect mobility strongly increases with increasing conductivity of the organic semiconductor. Moreover, by comparison with literature data on a variety of amorphous organic semiconductors, we propose that these two quantities and the dopant concentration may be linked by a universal empirical relationship. A tentative explanation based on the notion of electrical transport being dominated by hopping between localized states is given. A consequence is that large on/off ratios and high mobilities are not to be expected simultaneously in conventional MISFETs constructed from amorphous organic semiconductors.

Organic n-type field-effect transistor

Abstract We have used tetracyanoquinodimethane (TCNQ) as the active semiconducting material in metal-insulator-semiconductor field-effect transistors (MISFETs). TCNQ behaves as an n-type semiconductor. Differential capacitance measurements on metal-insulator-semiconductor (MIS) devices confirm the n-type behaviour. A maximum field-effect mobility of 3 × 10 −5 cm 2 V −1 s −1 is observed. On exposure to air the on/off ratio of the FETs improves to in excess of 450, due to oxidative dedoping of the TCNQ and narrowing of the channel.

Large induced optical activity in the conduction band of polyaniline doped with (1S)-(+)-10-camphorsulfonic acid

Abstract A large induced circular dichroism is found in the conduction band of polyaniline doped with optically active camphorsulfonic acid. In films obtained by spin-coating from a meta -cresol solution, the chiral dopant induces chirality within the main chain of polyaniline. No other combinations of achiral conducting polymers and chiral dopants have been found that show induced optical activity in their conduction band.

SELF-DOPED WATER-SOLUBLE CONDUCTING POLYMERS

Summaryα — Terthienyl and pyrrole, substituted with alkylsulfonate side chains, can be polymerized electrochemically without the addition of a conduction salt. This gives rise to self-doped conducting polymers that are soluble in water in the doped state.

The application of polypyrrole as counterelectrode in electrolytic capacitors

Abstract Solid electrolyte capacitors in which the counterelectrode MnO 2 is replaced by polypyrrole have been prepared and investigated. The dopant counterions of the polypyrrole electrode were varied and the influence on capacitor performance related to differences in material properties. This was verified both for zero-hour characteristics as for lifetime experiments at 125 °C in air. Capacitors with napthatlenesulfonate as counterion were very stable and showed an excellent high frequency performance, comparable with a ceramic multilayer capacitor.

Colourless nonlinear optical D-π-A polymers with sulphones as electron acceptors

Novel colourless side-chain methacrylate copolymers exhibiting relatively narrow charge-transfer bands at 335 nm and second-order optical nonlinearities up to d33= 4.3 pm V–1(at 1064 nm) have been synthesized and characterized.