Influence of the Bound Electron-Hole Pairs Dissociation Probability Field Dependence Form on the Photocurrent and Spatial Resolution of Organic Field Phototransistors

Abstract

In this work, numerical simulations are used to study ambipolar organic field-effect phototransistors, in which a spatially localized photoelectric effect can take place. This effect consists in the fact that there is a small spatially localized photosensitive region in the transistor channel, the position of which can be controlled by changing the gate voltage. The purpose of this work is to analyze the relationship between the form of the field dependence of the bound electron-hole pairs (𝑒/ℎ pairs) dissociation probability and characteristics of the studied ambipolar phototransistors such as normalized photocurrent, spatial resolution, and response time. It is shown that the optimal form of the field dependence of 𝑒/ℎ pairs dissociation probability is stepwise-like form, which can provide a high spatial resolution at high values of the normalized photocurrent without degrading the response time of the phototransistor. This shape can be achieved when the organic semiconductor has an extremely narrow distribution of 𝑒/ℎ pairs by size, described by the delta function. Also, on the example of several distributions of various shapes, it is shown that a decrease in the width of the distribution leads to an increase in the spatial resolution. Approaches to the selection and modification of organic semiconductor materials that would provide the most pronounced spatially localized photoelectric effect in ambipolar field-effect transistors are discussed.