Multicomponent seminconducting polymer systems with low crystallization-induced percolation threshold (NETSOMA)
The groups of Rene A.J. Janssen, Martin N. Nielsen, Henning Sirringhaus and Paul Smith of the CRP NETSOMA (Nanoscale Electrical Transport in Self-Organized Molecular Assemblies) have recently published a paper entitled ‘Multicomponent semiconducting polymer systems with low crystallization-induced percolation threshold’ which was a cover story in Nature Materials (Dec. 2006, Vol 5., 950- 956)
The paper presents the latest achievements reached by the CRP, through a wide collaboration that include the University of Cambridge, the ETH Zurich, TU Eindhoven and Riso National Laboratory.
This CRP's research focuses on exploring new electronic and optical phenomena arising in well-defined nanoscopic self-assemblies of bi-functional conjugated block copolymers. This CRP brings together four internationally leading groups with complementary expertise in conjugated polymer synthesis, polymer processing, structural characterisation of polymers and conjugated polymer device fabrication and device physics. Within this highly interdisciplinary and collaborative programme the partners have designed, prepared, processed, and characterised electrically, optically and structurally novel conjugated block copolymer architectures and self-assembled supramolecular block copolymers, and incorporated them into novel nanoscale electronic devices. Conjugated block copolymers are an ideal model system to study some of the fundamental interactions that control molecular self-assembly as well as to achieve sufficient control over the length scales and degree of self-organisation such that the electronic and optical properties of such molecular nanoscale assemblies can be studied.
This paper is the result of three years of work collaboration made possible through the SONS funding.Bicomponents blends comprising semicrystalline regioregular poly(3-Hexylthiophene) (P3HT) and selected semicrystalline commodity polymers have been investigated, and have shown that vertically stratified structures can be obtained in one-step process . Incorporating these as active layers in polymer field-effect transistors (FET) the concentration of the semiconductor can be reduced to values as low as 3 wt% without any degradation in device performance.
For blends made of P3HT and semicrystalline PE (Polyethylene) FET device performance was excellent for a concentration of P3HT as low as 3 wt%, and a value of mobility mFET of up to 6 x 10-2 cm2 V-1 s-1 was obtained.
Studies of temperature indicated also that the performance is temperature-dependent.
Clearly, excellent electronic performance can be obtained in crytstalline-crystalline bicomponent semiconductor-insulator polymer systems comprising less than 5 wt% of the semiconductor. Anyway, to achieve better performances the order in which the two components crystallise is fundamental.
More details of this research can be found in Nature Materials 5, 950 - 956 (2006). Nature Materials is the highest impact factor journal in the physical scieences.
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