Showing papers by "Rajib Chakraborty published in 2020"
TL;DR: In this work, various types of grating structures on both sides of active solar cell material for light trapping are studied in detail, and a new type of arrangement of optimized grating structure that significantly improves the light absorption is selected.
Abstract: Enhancement of optical to electrical conversion is vital for improving the efficiency of any solar cell. In recent years, use of thin films instead of bulk wafers has resulted in a huge reduction of production cost, and as such, efficiency enhancement of thin-film solar cells is considered in this study. Though this enhancement depends on several factors, most significant among them is the increase in light absorption within the active material of the solar cell. In this work, various types of grating structures on both sides of active solar cell material for light trapping are studied in detail, and a new type of arrangement of optimized grating structure that significantly improves the light absorption is selected. Enhancement of light absorption for change in dielectric material of the grating structure without changing the active material is also observed. Along with structural optimization, simulated electrical characterization of the samples was also performed, which yields a short-circuit current density of 29.27mA/cm2 with conversion efficiency of 14.51%, having a fill factor of 0.83 for a typical ultrathin layer of active material of thickness 2 µm. This is quite significant because typical cells of this category have much lesser conversion efficiency.
4 citations
TL;DR: In this article, a compact, dielectric-metal-dielectric surface plasmon polariton (SPP) waveguide is designed that can have propagation lengths as high as several thousand microns.
Abstract: A compact, dielectric–metal–dielectric surface plasmon polariton (SPP) waveguide is designed that can have propagation lengths as high as several thousand microns. The dielectric layers surrounding the metal waveguide are actually periodic layers of different nanometer-sized dielectric pairs. By proper selection of the surrounding layer widths, a device with a controllable effective index and increased compactness can be designed. It can have a propagation loss
3 citations
TL;DR: In this paper, a two dimensional square lattice photonic crystal (PhC) formed by placing glass matrix in air is proposed for subwavelength imaging around 840 nm.
Abstract: A two dimensional square lattice photonic crystal (PhC) formed by placing glass matrix in air is proposed for subwavelength imaging around 840 nm. The superlensing behavior at relatively lower wavelength compared to other reported PhC superlens is obtained by this configuration. Other advantages of using glass is that they have lower optical absorption at this wavelength and is relatively cheap. By placing the proposed PhC arrangement between the object and the objective of a conventional optical microscope, superlensing effect can be realized. Moreover, any change in radius of glass rod during fabrication process can result in the shift of superlensing wavelength.
1 citations
TL;DR: In this article, a spin-coated thin film with high refractive index (HRI) was used as an intermediate layer to enhance the light extraction efficiency (LEE) of a typical bottom-emitting organic light emitting diode (OLED).
Abstract: Studies on low-cost sol–gel spin-coated TiO2 thin film with high refractive index (HRI), which may be used as an intermediate layer to enhance the light extraction efficiency (LEE) of a typical bottom-emitting organic light emitting diode (OLED), are reported. The TiO2 solution is prepared using titanium tetra iso-propoxide, acetic acid, and ethanol. Spin coating method is used to deposit TiO2 thin films on glass substrate. Different optical characterizations of as-deposited and annealed (150°C, 300°C, and 450°C) TiO2 thin films on glass substrate are done, from which different properties of the film are derived. Ellipsometric measurement shows shrinkage in the thickness of the as-deposited TiO2 films after annealing at different temperatures. X-ray diffraction reveals amorphous TiO2 formation for all the samples. The RI of the coated film increases with the increase in annealing temperatures. Its value at 633 nm wavelength for the as-deposited film is found to be 2.1, which is quite high and it is seen that this RI can be further increased to 2.78 by annealing the samples at 450°C. This value is comparatively high compared to several other reported values of other researchers. The as-deposited sample reveals highest porosity, which further decreases with rise in annealing temperature. Our calculation of LEE for a typical OLED with the intermediate layer of this HRI as-deposited TiO2 film shows improvement of the LEE. However for annealed films, the experimentally obtained thicknesses are not adequate for this improvement, but it is shown that by increasing the film thickness, further improvement of LEE is possible.
1 citations
TL;DR: In this paper, a spin coated multilayer high refractive index TiO2 film developed on glass substrate was used to develop a sol-gel spin coated multi-layer high-refractive index (HRSI) TiO 2 film.
Abstract: Sol-gel spin coated multilayer high refractive index TiO2 film developed on glass substrate. The refractive index and band-gap can be altered by change the number of deposited layers.