Electronic properties of polypyrrole/n-Si heterojunctions and polypyrrole/metal contacts were investigated. Polypyrrole was electrochemically polymerized in 0.1 M pyrrole/0.05 M (rc-Bu)4NC1O4acetonitrile solution and polarized at various potentials to prepare samples with various contents of dopant. The sample polarized at the higher potential showed the higher content of C1O4-dopant and the higher spin density. The conductivity of polypyrrole increased with increasing dopant and spin density. The thermoelectromotive force suggested the characteristics of a p-type semiconductor. The I-V characteristics of polypyrrole/n-Si heterojunctions showed remarkable rectification. The contact between polypyrrole and a metal of low work function such as indium also showed rectification. These data also suggest p-type characteristics of polypyrrole. On the basis of electrical and optical data, the energy band diagrams of polypyrrole and the polypyrrole/n-Si heterojunction were discussed.
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