Abstract:Transient photocurrent in hydrogenated amorphous silicon is studied in all relevant time regimes following
the illumination of a pulse of light at one end of the sample. When both electron and hole transport are taken
into consideration, we find that, at a low occupation level of trap states or at a low intensity of illumination,
there are five well-defined current slopes. The first three are located at a short-time range, which has not
been probed experimentally, and they are due to the electron transport. Th… Show more
“…Relatively little work has been done to understand how space-charge effects influence current transients under the conditions of the presence of dispersive transport. Qualitative description of these effects can, however, be attempted on the basis of numerical simulations and simple considerations. 3 Variation of the dispersivity parameter α with temperature for a typical nanoparticle doped sample. 4 “Universal” curve obtained by superimposing several transients obtained for a sample of nanoparticle doped PVK at several voltages.…”
Section: Results Of Time-of-flight Measurements and Discussionmentioning
confidence: 99%
“…Relatively little work has been done to understand how space-charge effects influence current transients under the conditions of the presence of dispersive transport. Qualitative description of these effects can, however, be attempted on the basis of numerical simulations 48 and simple considerations. The original Scher-Montroll theory operates in the small signal approximation; thus, the electric field is considered constant and the drift velocity of carriers is considered to decrease in time because of the waiting time distribution ψ(t) ∝ t -R , leading to a time-dependent mobility.…”
Section: Results Of Time-of-flight Measurements and Discussionmentioning
Hybrid organic:inorganic materials have emerged as a novel class of electronic and optoelectronic media for a number of potential technological applications. However, very little fundamental understanding of charge carrier transport in such hybrid materials exists. A knowledge of the influence of nanoparticle doping on charge carrier mobility in nano composites becomes important in order to optimize properties for photorefractive and photovoltaic operations. We report here a study of the mobility of holes in a model nanoparticle-sensitized hybrid organic:inorganic system consisting of poly(N-vinylcarbazole) (PVK) doped with quantum dots of cadmium sulfide. The mobility of holes (dominant carriers in the PVK host materials) was measured using the conventional time-of-flight technique with injection of holes from a selenium layer. Though photocurrent transients exhibit features typical of dispersive transport in an amorphous semiconductor, certain deviations from the original Scher-Montroll theory are observed. Strong dependence of the carrier mobility on field and temperature indicate Poole-Frenkel-like activated hopping transport. A thickness dependence stronger than that suggested by the Scher-Montroll theory is found. Significant enhancement of the effective carrier mobility is noticed with the increase of nanoparticle concentration, still well below the percolation limit. A simple theoretical model based on time-and mean-free-path dependent mobility is proposed to account for this surprising result, which provides a good fit to the experimental data obtained.
“…Relatively little work has been done to understand how space-charge effects influence current transients under the conditions of the presence of dispersive transport. Qualitative description of these effects can, however, be attempted on the basis of numerical simulations and simple considerations. 3 Variation of the dispersivity parameter α with temperature for a typical nanoparticle doped sample. 4 “Universal” curve obtained by superimposing several transients obtained for a sample of nanoparticle doped PVK at several voltages.…”
Section: Results Of Time-of-flight Measurements and Discussionmentioning
confidence: 99%
“…Relatively little work has been done to understand how space-charge effects influence current transients under the conditions of the presence of dispersive transport. Qualitative description of these effects can, however, be attempted on the basis of numerical simulations 48 and simple considerations. The original Scher-Montroll theory operates in the small signal approximation; thus, the electric field is considered constant and the drift velocity of carriers is considered to decrease in time because of the waiting time distribution ψ(t) ∝ t -R , leading to a time-dependent mobility.…”
Section: Results Of Time-of-flight Measurements and Discussionmentioning
Hybrid organic:inorganic materials have emerged as a novel class of electronic and optoelectronic media for a number of potential technological applications. However, very little fundamental understanding of charge carrier transport in such hybrid materials exists. A knowledge of the influence of nanoparticle doping on charge carrier mobility in nano composites becomes important in order to optimize properties for photorefractive and photovoltaic operations. We report here a study of the mobility of holes in a model nanoparticle-sensitized hybrid organic:inorganic system consisting of poly(N-vinylcarbazole) (PVK) doped with quantum dots of cadmium sulfide. The mobility of holes (dominant carriers in the PVK host materials) was measured using the conventional time-of-flight technique with injection of holes from a selenium layer. Though photocurrent transients exhibit features typical of dispersive transport in an amorphous semiconductor, certain deviations from the original Scher-Montroll theory are observed. Strong dependence of the carrier mobility on field and temperature indicate Poole-Frenkel-like activated hopping transport. A thickness dependence stronger than that suggested by the Scher-Montroll theory is found. Significant enhancement of the effective carrier mobility is noticed with the increase of nanoparticle concentration, still well below the percolation limit. A simple theoretical model based on time-and mean-free-path dependent mobility is proposed to account for this surprising result, which provides a good fit to the experimental data obtained.
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