Abstract
Photoconductivity has been observed in high-purity tetracyanoquinodimethan (TCNQ) single crystals and polycrystalline evaporated thin films. The photocurrent was measured as a function of wavelength, light intensity, and temperature. A photoconducting edge is observed at about 1.7 eV. The spectral response of the crystals and films are essentially identical. Comparison with optical-absorption, reflection, and resistivity data imply that the 1.7-eV edge is a measurement of the band gap. The relatively small value is attributed to the high electron affinity of TCNQ and its polaron binding energy. Pulsed photocurrent measurements give a drift mobility for both electrons and holes of about 0.4 cm2/V sec in single crystals and somewhat lower in thin films. The electron mobility is about 10% higher than the hole mobility, and both are independent of temperature from 204 to 306 °K. The results suggest that conduction occurs by diffusion of small polarons in a conduction band whose width is comparable to the phonon energies. The relevance of this study to other systems is discussed.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 3560-3568 |
| Number of pages | 9 |
| Journal | Physical Review B |
| Volume | 10 |
| Issue number | 8 |
| DOIs | |
| State | Published - 1974 |
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ASJC Scopus subject areas
- Condensed Matter Physics
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Photoconductivity and small-polaron effects in tetracyanoquinodimethan. / Bright, A. A.; Chaikin, P. M.; McGhie, A. R.
In: Physical Review B, Vol. 10, No. 8, 1974, p. 3560-3568.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Photoconductivity and small-polaron effects in tetracyanoquinodimethan
AU - Bright, A. A.
AU - Chaikin, P. M.
AU - McGhie, A. R.
PY - 1974
Y1 - 1974
N2 - Photoconductivity has been observed in high-purity tetracyanoquinodimethan (TCNQ) single crystals and polycrystalline evaporated thin films. The photocurrent was measured as a function of wavelength, light intensity, and temperature. A photoconducting edge is observed at about 1.7 eV. The spectral response of the crystals and films are essentially identical. Comparison with optical-absorption, reflection, and resistivity data imply that the 1.7-eV edge is a measurement of the band gap. The relatively small value is attributed to the high electron affinity of TCNQ and its polaron binding energy. Pulsed photocurrent measurements give a drift mobility for both electrons and holes of about 0.4 cm2/V sec in single crystals and somewhat lower in thin films. The electron mobility is about 10% higher than the hole mobility, and both are independent of temperature from 204 to 306 °K. The results suggest that conduction occurs by diffusion of small polarons in a conduction band whose width is comparable to the phonon energies. The relevance of this study to other systems is discussed.
AB - Photoconductivity has been observed in high-purity tetracyanoquinodimethan (TCNQ) single crystals and polycrystalline evaporated thin films. The photocurrent was measured as a function of wavelength, light intensity, and temperature. A photoconducting edge is observed at about 1.7 eV. The spectral response of the crystals and films are essentially identical. Comparison with optical-absorption, reflection, and resistivity data imply that the 1.7-eV edge is a measurement of the band gap. The relatively small value is attributed to the high electron affinity of TCNQ and its polaron binding energy. Pulsed photocurrent measurements give a drift mobility for both electrons and holes of about 0.4 cm2/V sec in single crystals and somewhat lower in thin films. The electron mobility is about 10% higher than the hole mobility, and both are independent of temperature from 204 to 306 °K. The results suggest that conduction occurs by diffusion of small polarons in a conduction band whose width is comparable to the phonon energies. The relevance of this study to other systems is discussed.
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U2 - 10.1103/PhysRevB.10.3560
DO - 10.1103/PhysRevB.10.3560
M3 - Article
VL - 10
SP - 3560
EP - 3568
JO - Physical Review B-Condensed Matter
JF - Physical Review B-Condensed Matter
SN - 1098-0121
IS - 8
ER -