Improved Optical and Electronic Properties of Single-Layer MoS2 by Co Doping for Promising Intermediate - Band Materials

Owing to its unique optical and electronic characteristics, two-dimensional MoS2 has been widely explored in the past few years. Using first-principle calculations, we shed light on that the substitutional doping of Co can induce the half-filled intermediate states in the band gap of monolayer MoS2. The calculated absorption spectrum presents an enhancement of the low-energy photons (0.8 eV–1.5 eV), which is desired for intermediate-band solar cells. When the doping concentration increases, the reflectivity of the infrared and visible light (0.8 eV-4.0 eV) reduces, resulting in an improved photovoltaic efficiency of the material. Our results shed light on the application of heavily Co-doped MoS2 as intermediate band solar cell material.

Approaching Disordered Quantum Dot Systems by Complex Networks with Spatial and Physical-Based Constraints

This paper focuses on modeling a disordered system of quantum dots (QDs) by using complex networks with spatial and physical-based constraints. The first constraint is that, although QDs (=nodes) are randomly distributed in a metric space, they have to fulfill the condition that there is a minimum inter-dot distance that cannot be violated (to minimize electron localization). The second constraint arises from our process of weighted link formation, which is consistent with the laws of quantum physics and statistics: it not only takes into account the overlap integrals but also Boltzmann factors to include the fact that an electron can hop from one QD to another with a different energy level. Boltzmann factors and coherence naturally arise from the Lindblad master equation. The weighted adjacency matrix leads to a Laplacian matrix and a time evolution operator that allows the computation of the electron probability distribution and quantum transport efficiency. The results suggest that there is an optimal inter-dot distance that helps reduce electron localization in QD clusters and make the wave function better extended. As a potential application, we provide recommendations for improving QD intermediate-band solar cells.

Overcoming the Temperature Effect on a Single Junction and Intermediate Band Solar Cells Using Optical Filter and SECs

The performance of electronic devices, especially solar cells, at high temperatures is of primary interest to researchers. The design and construction of high-efficiency solar cells face some difficulties. One of these difficulties is the rising temperature, thus solar cells temperature assessment is essential to guarantee high performance. Normally, rising temperature, in solar cells, is associated with the normal ambient temperature and the produced internal temperature due to power dissipation. Accordingly, this investigation aims to reduce the effect of applied temperature from both sources. To reduce the destructive effect, the authors design a simple construction model that utilizes SiO2 and Si3N4 as a filtering layer. The outcomes of this study show that the power conversion is optimum. Si and SiC Solar cells both with and without using a filter are evaluated and compared. Finally, enhancement in power conversion efficiency and other characteristics has been investigated. The intermediate band solar cells were evaluated with both internal and external temperature effects. To reduce the internal temperature, the authors utilized a novel method for extracting the hot carriers from different energy levels by using multilevel energy selective contacts (ESCs). It was shown that ESCs promote efficiency and break the Shockley-Queisser limit.

The Effect of Noise-Induced Quantum Coherence in the Intermediate Band Solar Cells

It has been shown that quantum coherence induced by incoherent light can increase the efficiency of solar cells. Here we evaluate the effect of such coherence in the intermediate band solar cells. We first examine a six-level quantum IBSC model and demonstrate by simulation that the maximum of output power in a solar cell with quantum structure increases more than 16 percent in the case of coherence existence. We then propose an IBSC model which can absorb continuous spectra of sunlight and show that the quantum coherence can increase the output power of the cell. For instance, calculations indicate that the coherence makes an increase of about 31% in the maximum output power of a cell that the width of the conduction and intermediate bands are 100 and 10 meV, respectively. Also, our calculations show that the quantum coherence effect is still observed in increasing the solar cell power by expanding the width of the conduction band, although the output power is reduced due to increase in the thermalization loss. However, expanding the width of the intermediate band reduces the coherence effect.