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| Content Provider | IEEE Xplore Digital Library |
|---|---|
| Author | Furukawa, Y. Tasumi, M. |
| Copyright Year | 1994 |
| Description | Author affiliation: The University of Tokyo (Furukawa, Y.) |
| Abstract | Optical absorption spectroscopy is used for the identification of polarons and bipolarons in conducting polymers. We will reexamine the electronic absorptions due to polarons and bipolarons within the framework of a one-electron picture by using the data of the radical cations and dications of /spl alpha/-oligothiophenes and those of the radical anions and dianions of p-oligophenyls. For a positive polaron two localized electronic levels, bonding and antibonding, are formed in the band gap and an electron is removed from the polaron bonding level. A positive polaron is expected to have three transitions: w/sub 1/, polaron bonding level /spl larr/ valence band; w/sub 2/, polaron antibonding level /spl larr/ polaron bonding level; w/sub 3/, polaron antibonding level /spl larr/ valence band. For a positive bipolaron another electron is removed from the bonding level. Thus, a positive bipolaron is expected to have two transitions: w/sub 1'/, bipolaron bonding level /spl larr/ valence band; w/sub 3'/, bipolaron antibonding level /spl larr/ valence band. Similarly, a negative polaron is expected to have three transitions and a negative bipolaron two transitions. On this basis, three-band-patterns in observed electronic spectra have been usually assigned to polarons and two-band patterns to bipolarons. On the other hand, the radical cation and dication of /spl alpha/-sexithiophcne, which are viewed as models of a positive polaron and a positive bipolaron, respectively, show two absorption bands and one band, respectively, in the visible-near infrared region. The radical anion and dianion of p-sexiphenyl also shows two bands and one band, respectively. In these model systems, the w/sub 3/ and w/sub 3'/ transitions are symmetry forbidden. The results of the model systems indicate that the w/sub 3/ and w/sub 3'/ transitions are very weak in contrast to the others. We will propose new assignments of electronic absorption spectra induced by doping: two-band patterns to polarons and one-band patterns to bipolarons. |
| Starting Page | 693 |
| Ending Page | 693 |
| File Size | 95454 |
| Page Count | 1 |
| File Format | |
| DOI | 10.1109/STSM.1994.836136 |
| Language | English |
| Publisher | Institute of Electrical and Electronics Engineers, Inc. (IEEE) |
| Publisher Date | 1994-07-24 |
| Publisher Place | Korea |
| Access Restriction | Subscribed |
| Rights Holder | Institute of Electrical and Electronics Engineers, Inc. (IEEE) |
| Subject Keyword | Spectroscopy Photonic band gap Electromagnetic wave absorption Semiconductor process modeling Bonding Optical polymers Electrons |
| Content Type | Text |
| Resource Type | Article |
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