Although organic semiconductors have received the most attention, the development of compatible passive elements, such as interconnects and electrodes, is also central to plastic electronics. For this, ligand-protected metal-cluster films have been shown to anneal at low temperatures below 250∘C to highly conductive metal films, but they suffer from cracking and inadequate substrate adhesion. Here, we report printable metal-cluster–polymer nanocomposites that anneal to a controlled-percolation nanostructure without complete sintering of the metal clusters. This overcomes the previous challenges while still retaining the desired low transformation temperatures. Highly water- and alcohol-soluble gold clusters (75 mg ml−1) were synthesized and homogeneously dispersed into poly(3,4-ethylenedioxythiophene) to give a material with annealed d.c. conductivity tuneable between 10−4 and 105 S cm−1. These composites can inject holes efficiently into all-printed polymer organic transistors. The insulator–metal transformation can also be electrically induced at 1 MV cm−1, suggesting possible memory applications.
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We thank NUS (Project 144-000-131-112) and A*STAR (Project 052-117-0030) for funding.
The authors declare no competing financial interests.
Supplementary information I, II and II; figures S1 and S2; tables S1 and S2 (PDF 581 kb)
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Sivaramakrishnan, S., Chia, PJ., Yeo, YC. et al. Controlled insulator-to-metal transformation in printable polymer composites with nanometal clusters. Nature Mater 6, 149–155 (2007). https://doi.org/10.1038/nmat1806
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