ИСТИНА

Organic light emitting transistors (OLETs) are perspective optoelectronic devices that combine the switching ability of organic field-effect transistors (OFETs) with the light-generation capability. OLETs have a potential application in lighting, displays and injection lasers technologies. Light generation in the OLET channel occurs at the electron-hole recombination zone with a typical width of 15 – 200 nm . The spatial position of this zone is controlled by the gate voltage VG. Both for practical applications and theoretical studies it is important to know the exact form of dependence of the spatial position of light emission zone on VG. In this work we study the VG dependence of light-emitting area position for OLETs based on single layer of polycrystalline (pc) or single crystalline (sc) oligothiophene-phenylene co-oligomers (TPCO) which have low band gap near 2.7 eV and high luminescence quantum yield up to 44% . OLETs are prepared on silicon substrates with electron and hole-injecting electrodes (Fig. 1). The transfer characteristics (Fig. 1c) demonstrate ambipolar behavior with rather low hysteresis and high hole and electron mobilities even in pc film. Fig. 1d shows an image of part of OLET sample, where the. Fig. 1e depicts an image of the same area captured without external light with a long exposure time during which nine different values of VG from -12 V to -8 V with a step of 0.5 V were successively applied. For OLETs with different channel length, width and thickness we extract dependences of light emission area spatial position on VG and compare them with results of modeling with the use of a simple drift-diffusion model. The obtained results are expected to contribute to better understanding of processes of charge injection, transport and recombination in organic semiconductors. This work was supported by Russian Science Foundation (project № 18-12-00499).