International Journal of

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We have studied light-induced birefringence (LIB) and surface relief grating (SRG) formation in the series of methylacrylate polymers. The effect of material structure such as length of photochromic side chain, glass transition temperature and molecular structure of azo units on LIB and SRG are studied. The optical formation of self-induced SRG on films of these materials is also presented.

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In this paper, we used the time-of-flight (TOF) of a charge packet, that injected by a voltage pulse to calculate the drift velocity and mobility of holes in organic semiconducting polymers. The technique consists in applying a voltage to the anode and calculating the time delay in the appearance of the injected carriers at the other contact. The method is a simple way to determine the charge transport properties of organic semiconductors. The effect of charge trapping mechanism on the carrier mobility in the organic layer is investigated and it was shown that at higher applied voltage, 100 V, hole mobility increases rapidly in comparison with lower applied voltage (50 V).

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In this paper, a thin film silicon solar cell with anti-reflection coatings on front surface and the combination of periodic grating and photonic crystal on its back surface has been considered. The thickness and number of anti-reflection coatings, as well as the geometric and physical parameters of photonic crystal and grating are optimized to increase the optical absorption of solar cell. The simulations have been performed using the finite difference time domain method with Lumercial software. The results show that the optical absorption of solar cell has been increased significantly by utilizing the anti-reflection coatings, photonic crystal and grating.

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This article examines the impact of graded-index reflectors (GIRs) constructed from cholesteric liquid crystals (CLCs) on the modification of escape-cone loss and the improvement of luminescent solar concentrator (LSC) efficiency. GIRs are comprised of a structure in which the refractive index changes gradually with a spatial function. In this study, the LSC is a planar optical waveguide made of Poly (methyl methacrylate) (PMMA) with dimensions of 5×5×0.5 cm³ and contains CH₃NH₃PbBr₃ perovskite material as a fluorophore. Two types of GIRs are employed at the bottom of the LSC: periodic and quasi-periodic GIRs. Periodic reflectors (PRs) have a refractive index matrix that gradually changes with a periodic sinusoidal function, while the refractive index matrix of the quasi-periodic reflectors (QPRs) gradually changes with a chirped sinusoidal function. To analyze the models of the study, Monte-Carlo and Finite-Difference Time-Domain (FDTD) methods were utilized in conjunction with experimental results. The results indicated that the reflection band of a PR exhibited the maximum overlap (lowest escape cone) with the dye emission spectrum when the mirror's reflection band underwent a redshift of 20 nm compared to the dye emission spectrum. On the other hand, the QPR generated a broader reflection band, resulting in complete overlap and higher efficiency. Moreover, GIRs enhanced sunlight absorption in the LSC by reflecting transmitted solar photons through it. The optical efficiency (OE) of the LSC increased by 12% (33%) once a periodic (quasi-periodic) reflector is utilized. Furthermore, GIRs reduced escape cone loss, thereby increasing reabsorption, and subsequently, the system selected a lower optimal concentration to minimize reabsorption losses.