Studies onI-V characteristics of dark and photoconduction in methylbixin

J. Phys. D: Appl. Phys.

1989

Dark conduction and photoconduction in crocetin have been studied as a function of applied field and temperature. The results suggest that a single discrete trapping level is involved in charge carrier generation and that this level is different for dark conduction and photoconduction. Space-charge-limited current theory has been used to evaluate various transport parameters. In crocetin two opposite activation processes are operative in photoconduction in the two temperature regimes. The negative activation energy at high temperature may indicate activated exciton trapping in deep traps. The dependence of photocurrent on light intensity suggests that carrier generation is by a one-photon process and is trap limited. The photoconductivity spectrum suggests two distinct mechanisms of photocarrier generation, one through photoinjection from the illuminated electrode and the other through direct electron-hole pair production.

Section: Temperature Dependence Of Dark Conduction and Photoconductionmentioning

confidence: 79%

“…The dielectric constant of p-carotene is 2.5 [13]. Using this value for the dielectric constant of crocetin, effective drift mobility may be calculated from equation (2) and also from equation (5). The value of no/B can be obtained from equation (4).…”

Section: Evaluation Of Some Transport Parametersmentioning

confidence: 99%

Carrier generation and transport in crocetin crystals in a sandwich cell: steady state semi- and photoconductivity measurements

J. Phys. D: Appl. Phys.

1989

Photoconductive properties of zeaxanthin in a sandwich cell

Ghosh

Proc. Indian Acad. Sci. (Chem. Sci.)

1990

Self Cite

Photoconduction decay in zeaxanthin in a sandwich cell has been measured as a function of applied field and temperature in longer time domains (5-35 s). The results show that the gap states decrease exponentially with characteristic temperature T, ,~, 450 K at an applied field of 1.77 • 103 V/cm. When the sample temperature is 293 K, T, is found to be voltage-dependent and follows the empirical relation T, ,~, A exp(-b 1I). "l~e field effect on T~ is suggested to arise from the field effect on trapping rate. Light intensity dependence of photocurrent satisfies the power law I~, oc 1~ with y varying between 0"61 and 0-58 depending on the applied voltage at low excitation light intensity. At high intensities ~, = 1'2. 7", values evaluated from decay and light intensity dependence measurements show excellent correlation.

Charge transfer complexes of polyenes: spectroscopic, dark and photoconductive studies

J. Phys. D: Appl. Phys.

1990

Formation of molecular charge transfer (CT) complexes of some polyenes with iodine has been confirmed by spectroscopic studies. The dark and photoconductive properties of these CT complexes have been investigated in a sandwich cell. Both the dark and photoconductivity increases by several orders of magnitude by complex formation. The measured thermal activation energy is identical for dark and photoconduction in the complexes. Similar photoconduction action spectra in pure and in iodine-complexed polyenes suggest the same photocarrier generation mechanism to be operative in both the cases. Spontaneous generation of carriers by CT interaction and their migration by trapping and detrapping mechanisms seems to be responsible for electrical conduction in the CT complexes.