Sublinear Photocurrents and Surface Recombination in Cadmium Sulfide Crystals

Abstract

A model has been developed which adequately describes the sublinear photoresponse to strongly absorbed light in sensitized CdS. This model does not involve electron or hole trapping but rather postulates monomolecular bulk recombination and bimolecular surface recombination. Sublinear photocurrents are produced in this model whenever the ambipolar diffusion length is more than five times the penetration depth for the radiation. The results of measurements on sensitized CdS for temperatures between 90°K and 300°K will be presented which agree very well with this model when the electron and hole mobilities and hole lifetime determined by Spear and Mort are used as parameters in the model. The model also predicts many features of the photoresponse of sensitized CdS to weakly absorbed light, and provides a quantitative correlation between the bulk sensitivity, the surface recombination rate, and the peak in the photoresponse observed at the absorption edge. For the samples investigated, copper-compensated sensitized CdS platelets, the ambipolar diffusion length was found to be 6.2X10 -4 cm at 300°K.

High‐Performance Photodiode Based on Atomically Thin WSe2/MoS2 Nanoscroll Integration

“…Actually, the surface recombination effects play important role in determining the optoelectrical characteristics. The exponent k in the I ph ∼ P relationship is generally within the range of 0.5–1, where k = 0.5 indicates that bimolecular recombination mode is dominant while k = 1 suggests monomolecular recombination is dominant mode . In this device, both recombination modes exist, while the applied bias voltage could reduce the surface recombination effects probably due to the enhanced internal potential in the heterojunction region.…”

“…The exponent k in the I ph ∼ P relationship is generally within the range of 0.5-1, where k = 0.5 indicates that bimolecular recombination mode is dominant while k = 1 suggests monomolecular recombination is dominant mode. [44] In this device, both recombination modes exist, while the applied bias voltage could reduce the surface recombination effects probably due to the enhanced internal potential in the heterojunction region. Benefiting from the suppressed dark current (less than 10 −12 A), the important parameter-on/off ratio of photocurrent to dark current (signal to noise ratio)-could exceed 10 2 , which is nearly two orders of magnitude higher than the single MoS 2 nanoscroll photodetector at the same illumination condition.…”

Liquid Crystal-on-Organic Field-Effect Transistor Sensory Devices for Perceptive Sensing of Ultralow Intensity Gas Flow Touch

“…As a result, both rise and decay time constants (τ), which were obtained by fitting with the I D – time (t) plot (Fig. 3a) based on a single exponential rise/decay equation (see the method part in detail)2728, were gradually decreased as the gas flow touch time increased (Fig. 3b right).…”

Photocurrent limit in nanowires

“…(1) holds and I PC ∝ I in 0.5 at high illumination levels is expected to be observed [4]. On the other hand, three-dimensional crystals, where diffusion takes place, do not show the square root law at high illumination levels, but dependences with Θ 0.65-0.80 [14].…”