ORËL ResearchLab

Organic electronics is a relatively young interdisciplinary field at the intersection of chemistry, physics, biomedicine and technology. Having originated at the end of the 20th century, it continues to develop rapidly due to the huge potential of organic semiconductors, which have a number of undeniable advantages in comparison with traditional inorganic semiconductors. Such advantages include lightness, solubility, variability of properties, cheaper manufacturing technology for electronics devices and biocompatibility (OLED). One of the most striking examples of this development is organic light–emitting diodes, which appeared on the market for the first time 15 years ago and are currently used everywhere, having firmly conquered the niche of display devices. Such rapid development has fueled the interest of researchers around the world in the development of fundamental research related to the establishment of the nature of light emission and semiconductivity in organic molecules, their interaction with the environment in order to obtain even more efficient materials and devices. Since 2012, thermally activated delayed fluorescence (TADF) emitters have attracted the attention of researchers in connection with their use in (OLED), replacing expensive phosphorescent emitters based on atoms of rare and expensive noble metals. Such emitters have a small difference between singlet and triplet levels (ΔEST), which promotes reverse intercombination conversion (RISC) from T1 to S1 state. Traditional TADF emitters are based on the spatial separation of donor (D) and acceptor (A). This makes it possible to spatially separate the electron densities of the highest occupied molecular orbital (VSMO) and the lowest unoccupied molecular orbital (NSMO), which leads to a decrease in the value of EST. Nevertheless, most TADF emitters, despite their amazing characteristics in all color ranges, exhibit significant structural relaxation in the excited state, a large Stokes shift, and wide emission spectra (FWHM > 50 nm) characteristic of intramolecular charge transfer (ICT). Unfortunately, such wide emission spectra do not allow achieving high purity of the OLED display color rendering. In order to achieve the required color purity, OLED emission is required to be represented by an extremely narrow-band emission spectrum FWHM < 15 nm, which is difficult to achieve for classical donor-acceptor TADF emitters. In 2016, Hatakeyama et al. presented a new molecular design concept based on the effect of multiple resonance of boron (B) and nitrogen (N) atoms, using the example of the developed DABNA emitter. In such structures, the separation of VSMOS and NSMOS is achieved due to opposite resonant effects in the same rigid π-conjugate system. The short-range nature of charge transfer between electron acceptor boron atoms and electron-donating nitrogen atoms located in ortho- and para-positions relative to them, combined with the rigidity of the structure, made it possible to achieve narrowband emission (FWHM < 30 nm), small Stokes shift, low reorganization energy and high quantum yield of photoluminescence. This makes such dyes very promising for use in next-generation OLEDs. Nevertheless, the search for new MR-TADF structures is a rather time-consuming task, which is due to the fact that resource-intensive calculation schemes based on Coupled cluster methods are used to predict the properties of MR-TADF, and the synthesis of new structures is usually multistage and requires quite advanced methods. Thus, the search for new tools for the molecular design of MR-TADF emitters is a very urgent fundamental task facing researchers in the next 5 years. In this project, it is proposed to develop specialized neural networks for accelerated prediction of optoelectronic properties of new structural motifs with the effect of multiple resonance, to develop methods for the synthesis of the most promising molecules for use in organic optoelectronics applications, including unique approaches based on the introduction of spirocyclic fragments into the molecular structure with the MR-TADF effect, which will allow to obtain narrowband emitters with high the purity of the color. In addition to optoelectronic applications, organic electronics, being biocompatible and hybrid, can be used for bioelectronics devices, for example, implantable sensor devices or the creation of artificial synapses and their networks based on neuromorphic transistors. Particular interest in the latter has arisen due to the fact that the growth of big data and the Internet of Things (IoT) places higher demands on computing speed and power consumption of a computer system. Unfortunately, traditional computers based on the von Neumann architecture face bottlenecks caused by the physical separation of memory and CPU and high power consumption. Therefore, a more efficient computing system with low power consumption and high data density is in great demand today. Compared with traditional computers, the human brain processes information in a high-speed parallel way with high fault tolerance and energy efficiency (~20 watts). Therefore, the development of neuromorphic computing devices that can mimic the functions of the human brain is currently becoming one of the most relevant areas of research. The human brain consists of ~1011 neurons and ~1015 synapses. Synapses act as bridges connecting neurons and forming a complex neural network that endows the brain with unique functions. Thus, the manufacture of artificial synaptic devices is the physical basis for the construction of neuromorphic computing networks. Various types of devices such as memristors, atomic switches, phase transition memory (PCM) and field effect transistor (FET) have been successfully used as artificial synapses to simulate biological synaptic functions.