Kinetics of the persistent photocurrent in a-Si:H

Abstract

Although the persistent photocurrent (PPC) in amorphous hydrogenated amorphous silicon (a-Si:H) is known to be dominated by dispersive recombination kinetics which produce the power low decay, [Formula: see text], where [Formula: see text] is the dispersion parameter, the reason for the occurrence of the dispersive reaction is not clear. We discuss the origin of the dispersive nature in the PPC in a-Si:H. It is shown that band edge modulation due to microscopic inhomogeneity may play an important role in the PPC dynamics.

Influence of oxygen assisted recombination on persistent photocurrent characteristics of ZnO polycrystalline thin films prepared by RF magnetron sputtering

“…23) K. Sakaguchi et al reported the reaction model in which exact electrons or holes encounter oxygen molecules with waiting time dispersion at the surface for PPC phenomena in the oxygen ambient for TiO 2 materials. 24,25) In the train of inhomogeneous media analysis reported previously on the without-surface-reaction, here we present a report on the PPC in the case of with-surface-reaction by the oxygen gas atmospheres. The phenomenological model could be derived the behavior of reaction between electrons, holes, and oxygen molecules on the surface of ZnO film.…”

“…R is the average value resulted from the Poisson distribution in perfect random encountering phenomena. For the oxygenassisted recombination, the waiting time (t′) for encountering oxygen at the surface of ZnO thin film is proposed in term of thermal energy (E A ) as in the following equation; 24,25) t…”

“…Equation (7) shows the waiting time probability function depended on time. We can define as the expected value of the average waiting time á ñ t ( ) as the following; 25)…”

Persistent photocurrent characteristics of ZnO polycrystalline films prepared by RF magnetron sputtering

“…From theoretical considerations, bimolecular recombination processes are allowed, taking into account the rate equation for electrons and holes excited by the illumination. 31,32) These saturation levels will be determined by the final recombination between electrons and holes regardless of the intermediate recombination steps and processes.…”

“…34) These features have also been observed in inhomogeneous media such as amorphous semiconductors. 25,32,35) Recombination processes of the excited carriers must occur near the area where holes are traps. The carrier activation energy required for recombination can be effectively estimated as potential fluctuations Δ ∼ .…”