Nanocomposites and nanomaterials

Optimization of photoelectric converters
Beliak Ie.V.1, Kryuchyn A.A.1, Manko D.Yu.1
1 Institute for Information Recording of the NAS of Ukraine. M. Shpak, str 2, Kyiv-03113, Ukraine. 
E-mail: beliak1312@gmail.com

The improvement of the efficiency of photovoltaic converters (Power Electronic Transformer, PET) which absorbs solar radiation in the visible and near infrared ranges of the spectrum is relevant for the creation of a new generation of solar photovoltaic systems and optical channels energy transmission optoelectronic systems [1-2]. It should be also noticed that optimization of the characteristics of optoelectronic systems is one of the most important areas in the field of organization of optical monitoring and data transmissions systems. Compact camera units, which today are actively included in the composition of general-purpose electronic devices and, in particular, mobile devices due to the simplification of the optical photo-registration system are characterized by relatively low photosensitivity and imbalance of color rendering scheme. The concept of the luminescent solar concentrator has emerged as an efficient approach to harvesting sunlight economically, able to overcome the factors that limit the conversion efficiency of photovoltaic systems. LSCs (luminescent solar concentrator) consist of a layer containing optically active centers applied to a transparent substrate, which, when exposed to light, converts part of the absorbing radiation corresponding to the short-wave visible and ultraviolet part of the solar spectrum into radiation of a certain wavelength corresponding to the PET absorption spectrum. While part of the emitted signal will be lost at the surface (through the so-called exit cone), the rest will be trapped inside the layer and substrate and directed towards the edges (through total internal reflection) where it can be collected by the photovoltaic cell. Various optically active centers have been tested in LSC, including organic dyes, quantum dots, and trivalent lanthanide ions [3]. 
An effective way to optimize the characteristics of PET can be the application of photoluminescent layers based on nanostructured photoluminescent dyes with fixed Stokes shear and photoluminescence range, selected according to the absorption spectra of photovoltaic components of triad and tetrads of the photoelectric transducers. Conventional dyes often suffer from a low photoluminescence quantum yield, insufficient photostability, and a insufficient Stokes shift. In other hand the use of organic dye nanoparticles provides efficient luminescence’s resonance energy transfer with markedly improved imaging performance. Currently, the most widely used organic dyes, which are usually encapsulated in various nanoparticles to overcome the internal limitations of conventional dyes, including poor hydrophilicity, low photostability, low quantum yield. Compared to pure dyes, organic dye nanoparticles have an almost 50-fold increased quantum yield, large Stokes shifts (∼250 nm), and significantly increased photostability [3]. The general principle of optimizing the photoelectric conversion process by applying a photoluminescent layer to the elements of the photo matrix is to transfer radiation to the absorption region of the photoelectric converter — thus, the Stocks shift of the photoluminescent dye should be equal to the difference between the main peak of solar spectrum and the photoelectric converter absorption spectrum. 
Obtaining the characteristics of the luminescent converter determined as a result of mathematical modeling is carried out through the use of the procedure of nanostructuring the organic photoluminescent dyes with zeolite pores, laser annealing, and the inclusion of impurities of polymeric materials (polymethyl methacrylate, polystyrene and others). Based on the study, the effectiveness of improving the photosensitivity and color rendering of photodetection systems by expanding the absorption spectrum of photocells was proved and the value of Stokes shift of photoluminescent materials of the coating layer for color channels was calculated.

1.	Lu Q., Shuhong Xu. S., Haibao Shao H. et al Improving power conversion efficiency in luminescent solar concentrators using nanoparticle fluorescence and scattering // Nanotechnology. – 2020. - 31. - P. 45-52.
2.	Griffini G.  Host Matrix Materials for Luminescent Solar Concentrators: Recent Achievements and Forthcoming Challenges // Frontiers in Materials. - 2019. - 6, N 29. doi:10.3389/fmats.2019.00029.
3.	Yu J., Zhang X., Hao X., Zhang X.  et al. Near-infrared fluorescence imaging using organic dye nanoparticles // Biomaterials.- 2014. - 35, N 10. - P. 3356–3364.