ИСТИНА

Organic phototransistors are similar in structure to field-effect transistors, they consist of layers of an organic semiconductor (active layer), a dielectric layer, and have three electrodes – the source, drain and gate (Fig. 1, left). Phototransistors combine the properties of field-effect transistors and photodiodes. Efficient phototransistors should be ambipolar to allow all photogenerated electrons and holes to contribute to the photocurrent. In this work organic phototransistors with high spatial resolution are proposed. Under high spatial resolution it is implied the presence of a photosensitive area with small width w along x-axis much lower than channel length L, which spatial position along x-axis can be controlled by the gate voltage. Such photosensitive area in the channel of the ambipolar phototransistor can be formed in depleted area between areas with high electron and hole concentrations n and p, and where the electric field Ex reaches its maximum (Fig. 1, right). High electric field facilitates efficient separation of electron-hole pairs (excitons), therefore light absorbed in this area will give maximal contribution to the photocurrent. From the literature data it is known that the width of the transition region reaches 15-200 nm in ambipolar organic field-effect transistors [1]. In this work, using a simple one-dimensional drift-diffusion numerical model, the phototransistor response to the non-homogenously distributed along x-axis light is studied and optimal material parameters for high spatial resolution are discussed. This work was supported by Russian Science Foundation (project 18-79-00341).