Metastable light induced effects in pentacene

• Instability mechanism of pentacene thin film under light illumination is analyzed.
• Light affects pentacene performance depending on wavelength and photon dose.
• Deep states in pentacene thin film contribute to persistent photocurrent.
• Ultraviolet light generates metastable defects in pentacene thin film.
• A model describing the dynamics of UV-light induced defects is proposed.

In this study, one of the environmental factor which could affect organic materials was analyzed. Pentacene thin film samples were fabricated and the stability of their electrical properties was monitored when the devices were exposed to different energy light sources. Steady-state photocurrent spectrum and transient behavior were investigated in order to explore the dispersive transport mechanism and the carrier trapping and recombination effects. Anomalous phenomena were revealed for effect of a persistent ultraviolet (UV) irradiation, in particular a photoconductivity degradation under light conditions and a dark recovery, whose evolutions were studied focusing on the metastable nature of defects. The results were reported in terms of a trap density model, which provides a description of the dynamics of light induced electrically active defects in an organic semiconductor.

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