Studies of photoconductivity in β-Apo-8′ carotenal

Abstract

The photoconductive properties of a carotenoid polyene,/%Apo-8' carotenal in polycrystalline form has been studied. The growth of the photoeurrent shows an overshoot in the growth-time curve before steady state value is attained. This behaviour of photocurrent is proposed to be due to higher value of recombination coefficient than trapping coefficient. From the temperature dependence study it is observed that the steady state photocurrent, at first increases with increase of temperature, attains a maximum at a particular temperature Tma x and then decreases with temperature. The T,,,x value agrees with the temperature above and below which steady state photocurrent is attained differently. Monomolecular and bimolecular recombination processes at two temperature regimes are proposed to account for the observed behaviour. The dependence of photoeurrent with excitation light intensity and wavelength study provide information on the carrier generation processes. The fast decay of photocurrent have been observed at different temperatures and from this study the decay constant is calculated and it is found to be temperature independent.geywords. Polyene; organic photoconductivity; action spectra; growth and decay kinetics.

Organic optoelectronic interfaces with anomalous transient photocurrent

“…This situation is quite different from that in the b-Apo-8 0 carotenal devices 69 where both J tr and J st are dominated by bimolecular recombination. It was noted that the BDTDA devices exhibited good rectification (B10 2 at AE2 V) in their current-voltage curves.…”

“…b-Apo-8 0 carotenal was reported to exhibit such anomalous behaviour in 1996. 69 However, only the anomalous rise in photocurrent was investigated by studying the temperature and light intensity dependence. A threshold temperature T max was observed, below which, the photocurrent rises slowly to attain a steady-state photocurrent without experiencing an overshoot.…”