ИСТИНА

Organic light-emitting transistors (OLETs) are novel type of devices which combine light-emitting properties of organic LEDs and electrical switching ability of organic field-effect transistors . OLETs contain an organic semiconductor active layer and a dielectric layer and have three electrodes: source, drain and gate (Fig 1a,b). Source injects holes and drain injects electrons into active layer, where electrons and holes recombine, as a result the photons are emitted. By changing the gate voltage the drain-source current can be tuned, therefore the emitted light intensity can also be changed. The OLET efficiency of power conversion from electricity to light is higher than for organic LEDs but is still lower if compared with inorganic LEDs, partly because of lack understanding of OLET device physics, especially the main energy loss channels. Existing theoretical studies on OLETs do not consider its power conversion efficiency (PCE). This work is devoted to calculation of OLET PCE and quantum efficiency by means of numerical modeling. -- Fig. 1. (a) Scheme of OLET, active layer is shown by yellow rectangle. (b) Band diagram of OLET channel. The values of electron affinity χ, band gap Eg, dielectric permittivity ε, hole and electron mobilities µh,e are given. (c) Dependences of OLET PCE on source-gate voltage Vg at source-drain voltage Vd=-4 V for different source and drain work functions AS and AD. In this work, we present a one-dimensional drift-diffusion numerical model of OLET and study the OLET performance for various parameters and properties of active layer and electrode materials. We have found that the OLET PCE is the most sensitive to the work functions of source and drain electrodes (Fig. 1c). In the same time, the most of geometrical and material parameters of the OLET (such as temperature, electron and hole mobilities, CS, channel length) give a far less pronounced effect on the OLET performance. We analyze the energy losses due to low carrier mobility, insufficient selectivity and high contact resistance of the electrodes, energetic disorder, and non-radiative recombination. Approaches for minimizing these losses are discussed. The results of this work can help to develop high-performance OLETs. This work was supported by Russian Science Foundation (project № 15-12-30031).