Opto-electrochemical spectroscopy oftrans- (CH)x

作者：Avi Y. Feldblum, James H. Kaufman, S. Etemad, Alan J. Heeger, T. C. Mike Chung, Alan Graham MacDiarmid · 发表于：Physical review. B, Condensed matter · 年份：1982 · DOI：10.1103/physrevb.26.815 · 被引用次数：182 · 研究领域：Conducting polymers and applications、Electrochemical Analysis and Applications、Analytical Chemistry and Sensors

Detailed quantitative studies of the visible near-ir absorption spectra of trans-${(\mathrm{CH})}_{x}$ have been carried out in the semiconducting, transitional, and metallic regimes. With the use of the opto-electrochemical technique to take advantage of the control and precision of electrochemical doping, the absorption data were obtained in situ, during the doping process. Thin ${(\mathrm{CH})}_{x}$ films were polymerized on conducting glass and used as one electrode in an electrochemical cell (${\mathrm{Li}}^{+}$Cl${\mathrm{O}}_{4}^{\ensuremath{-}}$ in propylene carbonate) with a strip of Li metal as the counter electrode. As the trans-${(\mathrm{CH})}_{x}$ was doped from $y<0.003$ to $y\ensuremath{\simeq}0.08$, the interband absorption peak decreased and the midgap absorption increased in intensity. The quantitative agreement with the calculations of the soliton model and the universal nature of the data provide direct evidence for the existence of charged solitons in doped trans-${(\mathrm{CH})}_{x}$. The results show that in the concentration range $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}<y<5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}$, where independent experiments have established that the high conductivity is due to spinless carriers, the semiconductor gap persists with little change in magnitude. Moreover, the absorption data identify these carriers as charged solitons. Kinetic studies following a step change in applied cell voltage i...