Sameh O. Abdellatif

Bio: Sameh O. Abdellatif is an academic researcher from British University in Egypt. The author has contributed to research in topics: Photovoltaic system & Energy conversion efficiency. The author has an hindex of 10, co-authored 56 publications receiving 257 citations. Previous affiliations of Sameh O. Abdellatif include Egypt Nanotechnology Center & Cairo University.

Thermoelectric Energy Harvesters: A Review of Recent Developments in Materials and Devices for Different Potential Applications

Abstract: The thermoelectric effect encompasses three different effects, i.e. Seebeck effect, Peltier effect, and Thomson effect, which are considered as thermally activated materials that alter directions in smart materials. It is currently considered one of the most challenging green energy harvesting mechanisms among researchers. The ability to utilize waste thermal energy that is generated by different applications promotes the use of thermoelectric harvesters across a wide range of applications. This review illustrates the different attempts to fabricate efficient, robust and sustainable thermoelectric harvesters, considering the material selection, characterization, device fabrication and potential applications. Thermoelectric harvesters with a wide range of output power generated reaching the milliwatt range have been considered in this work, with a special focus on the main advantages and disadvantages in these devices. Additionally, this review presents various studies reported in the literature on the design and fabrication of thermoelectric harvesters and highlights their potential applications. In order to increase the efficiency of equipment and processes, the generation of thermoelectricity via thermoelectric materials is achieved through the harvesting of residual energy. The review discusses the main challenges in the fabrication process associated with thermoelectric harvester implementation, as well as the considerable advantages of the proposed devices. The use of thermoelectric harvesters in a wide range of applications where waste thermal energy is used and the impact of the thermoelectric harvesters is also highlighted in this review.

Transparency and Diffused Light Efficiency of Dye-Sensitized Solar Cells: Tuning and a New Figure of Merit

Abstract: Tunability is considered one of the main advantages of dye-sensitized solar cells (DSSCs) over conventional Si-based solar cells. In DSSCs, the thickness of the active layer can tune the transparency of the cell. This, however, creates a tradeoff between the transparency and the cell's efficiency. DSSCs with tailored transparency would be capable of being utilized in photovoltaic window applications, where Si cells are barely suitable. In this article, a new figure of merit is introduced to evaluate the performance of the DSSCs, named “TED efficiency.” The proposed TED parameter (i.e., the transparency, conversion efficiency, and diffused light efficiency) not only is based on the cell conversion efficiency but also considers the optical transparency as well as the cell performance under diffused light. TED efficiency measurements were performed on three different types of DSSCs: standard (DSSC-A), simple semitransparent (DSSC-B), and scattering-enhanced DSSCs (DSSC-C). A 22.5%-transparent DSSC has been fabricated by reducing the thickness of the porous TiO2 layer. To optimize the TED efficiency of the semitransparent DSSC, an opaline SiO2 layer is used. This layer enhances the forward scattering, acts as an UV protecting layer, and colorizes the semitransparent cell in a decorative manner. The TED efficiency for the scattering-enhanced DSSC showed a significant improvement to the standard DSSC as well as to the semitransparent cell.

Simulating the dispersive behavior of semiconductors using the Lorentzian–Drude model for photovoltaic devices

Abstract: Unique light-trapping structures that improve the efficiency of thin-film solar cells require advanced computational methods that can simulate the propagation of light through the thickness of each material in the solar cell. The simulations community that uses the Lorentz–Drude (LD) model cannot precisely simulate the propagation of light through the entire spectrum of the Sun, due to the difficulty in extrapolating the coefficients of each solar cell material. In this paper, a new technique for modeling dispersive and absorptive material over the Sun’s entire wavelength range (200–1700 nm) using the LD model is suggested. The new numerical models are used for simulating light propagation through various one-dimensional light-trapping structures, including metal backreflectors and distributed Bragg reflectors. All the numerical simulation results show agreement with previously published theoretical and experimental results. The proposed simulation technique will help the simulations community in using the LD model to simulate the propagation of light in solar cells more accurately.

Experimental quantum key distribution beyond the repeaterless secret key capacity

Abstract: Quantum communications promise to revolutionise the way information is exchanged and protected. Unlike their classical counterpart, they are based on dim optical pulses that cannot be amplified by conventional optical repeaters. Consequently they are heavily impaired by propagation channel losses, which confine their transmission rate and range below a theoretical limit known as repeaterless secret key capacity. Overcoming this limit with today's technology was believed to be impossible until the recent proposal of a scheme that uses phase-coherent optical signals and an auxiliary measuring station to distribute quantum information. Here we experimentally demonstrate such a scheme for the first time and over significant channel losses, in excess of 90 dB. In the high loss regime, the resulting secure key rate exceeds the repeaterless secret key capacity, a result never achieved before. This represents a major step in promoting quantum communications as a dependable resource in today's world.

Profiling the Thermoelectric Power of Semiconductor Junctions with Nanometer Resolution

Abstract: We have probed the local thermoelectric power of semiconductor nanostructures with the use of ultrahigh-vacuum scanning thermoelectric microscopy. When applied to a p-n junction, this method reveals that the thermoelectric power changes its sign abruptly within 2 nanometers across the junction. Because thermoelectric power correlates with electronic structure, we can profile with nanometer spatial resolution the thermoelectric power, band structures, and carrier concentrations of semiconductor junctions that constitute the building blocks of thermoelectric, electronic, and optoelectronic devices.

Self-Powered Implantable Medical Devices: Photovoltaic Energy Harvesting Review.

Abstract: Implantable technologies are becoming more widespread for biomedical applications that include physical identification, health diagnosis, monitoring, recording, and treatment of human physiological traits. However, energy harvesting and power generation beneath the human tissue are still a major challenge. In this regard, self-powered implantable devices that scavenge energy from the human body are attractive for long-term monitoring of human physiological traits. Thanks to advancements in material science and nanotechnology, energy harvesting techniques that rely on piezoelectricity, thermoelectricity, biofuel, and radio frequency power transfer are emerging. However, all these techniques suffer from limitations that include low power output, bulky size, or low efficiency. Photovoltaic (PV) energy conversion is one of the most promising candidates for implantable applications due to their higher-power conversion efficiencies and small footprint. Herein, the latest implantable energy harvesting technologies are surveyed. A comparison between the different state-of-the-art power harvesting methods is also provided. Finally, recommendations are provided regarding the feasibility of PV cells as an in vivo energy harvester, with an emphasis on skin penetration, fabrication, encapsulation, durability, biocompatibility, and power management.