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

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.