Nanooptics and photonics
Kinetic and Electrostatic Control of Electroluminescence in Molecular Junctions
V. O. Leonov, Ye. V. Shevchenko, E. G. Petrov
Bogolyubov Institute for Theoretical Physics of NAS of Ukraine,
14-b Metrolohichna str. Kyiv, 03143, Ukraine
e-mail: leogluck@gmail.com 

Physically, electroluminescence (EL) can be observed during the resonant transmission of electrons from the -th electrode to the -th electrode. In such a process, energy  of excited singlet level of a molecule has to fall in the intervals  (1) or  (2) ( is the chemical potential of the -th electrode). The electrostatic control of EL is achieved by shifting the position of the energy levels  and  associated with a positively or negatively charged molecule. Thus, by changing the magnitude and polarity of  and , conditions are reached under which inequalities (1) and (2) are fully, partially, or not at all fulfilled. In addition, it is necessary to reduce the quenching of EL caused by the interaction of the fluorophore with the electrodes. This is achieved with the help of spacers that create tunnel barriers between the fluorophore and the surface of each of the electrodes.  A charge hopping through tunneling barriers is the determining factor controlling the kinetics of charge transmission processes in the 1F2 system. The corresponding hopping rates are expressed in terms of parameters  and ,which determine the broadening of the LUMO and HOMO levels respectively. In asymmetric 1F2 junctions where  and  can differ markedly in magnitude. Therefore, the kinetics of electron transfer significantly depends on the polarity , so that the EL becomes bipolar. The population of the excited singlet level of the molecule, , depends significantly on the voltage polarity. We have shown [1,2], that under conditions (1) and (2)  control over EL can be achieved via the  variation of . Thus, in addition to the electrostatic control of EL (via bias and gate voltages), a kinetic mechanism for regulating EL in photoactive nanoscale molecular junctions is proposed. 

1.	Леонов В. О., Шевченко Є. В., Петров Е. Г. Вплив потенціялу бази на електролюмінесценцію в молекулярній фотодіоді // Наносистеми, Наноматеріали, Нанотехнології.-2020.-18,-N 2.-P. 227-240.
2.	Petrov E. G., Leonov V. O., Shevchenko Ye. V. Control of electroluminescence in a molecular photodiode by gate voltage // Modern Physics Letters B.-2020.-34, N 18.-P. 2040063.