Optimization of a CNT-based SiGe Thin Film Solar Cell Structure

In this paper, a SiGe thin film solar cell structure based on the carbon nanotube (CNT) and with a back surface field (BSF) layer is proposed. The efficiency of this structure is 40.36%, which is higher than conventional structures without CNT layer. We optimize this structure by changing the base layer thickness and determining the ratio of the width of the upper contact to the width of the entire cell. The cell efficiency after this optimization reaches 41.08%. Furthermore, the performance of this cell is evaluated using two types of CNT layers with sheet resistances of 128 Ω/□ and 76 Ω/□. The results of numerical simulation show that the SiGe thin film solar cell using CNT layer with 128 Ω/□ sheet resistance has better performance parameters. Finally, the number of metal electrodes above the cell is optimized due to the shading effect and we show that the contact distance in the presence of CNT layer can be increased up to 2000 µm.

A Numerical Investigation on the Combined Effects of MoSe2 Interface Layer and Graded Bandgap Absorber in CIGS Thin Film Solar Cells

The influence of Molybdenum diselenide (MoSe2) as an interfacial layer between Cu(In,Ga)Se2 (CIGS) absorber layer and Molybdenum (Mo) back contact in a conventional CIGS thin-film solar cell was investigated numerically using SCAPS-1D (a Solar Cell Capacitance Simulator). Using graded bandgap profile of the absorber layer that consist of both back grading (BG) and front grading (FG), which is defined as double grading (DG), attribution to the variation in Ga content was studied. The key focus of this study is to explore the combinatorial effects of MoSe2 contact layer and Ga grading of the absorber to suppress carrier losses due to back contact recombination and resistance that usually occur in case of standard Mo thin films. Thickness, bandgap energy, electron affinity and carrier concentration of the MoSe2 layer were all varied to determine the best configuration for incorporating into the CIGS solar cell structure. A bandgap grading profile that offers optimum functionality in the proposed configuration with additional MoSe2 layer has also been investigated. From the overall results, CIGS solar cells with thin MoSe2 layer and high acceptor doping concentration have been found to outperform the devices without MoSe2 layer, with an increase in efficiency from 20.19% to 23.30%. The introduction of bandgap grading in the front and back interfaces of the absorber layer further improves both open-circuit voltage (VOC) and short-circuit current density (JSC), most likely due to the additional quasi-electric field beneficial for carrier collection and reduced back surface and bulk recombination. A maximum power conversion efficiency (PCE) of 28.06%, fill factor (FF) of 81.89%, JSC of 39.45 mA/cm2, and VOC of 0.868 V were achieved by optimizing the properties of MoSe2 layer and bandgap grading configuration of the absorber layer. This study provides an insight into the different possibilities for designing higher efficiency CIGS solar cell structure through the manipulation of naturally formed MoSe2 layer and absorber bandgap engineering that can be experimentally replicated.

Analysis increase in the efficiency of a-Si: H solar cell due to the addition of an intrinsic layer to the p-i-n structure by ellipsometric spectroscopy

Backround: In this study, we report for the first time that the addition of an intrinsic layer to the a-Si: H p-i-n solar cell structure greatly enhances the conversion efficiency. The a-Si: H p-i-n solar cells were grown using Plasma Enhanced Chemical Vapor Deposition (PECVD) techniques on the Indium Tin Oxide (ITO) substrate and added an intrinsic layer with the p-i1-i2-n structure in order to prevent sunlight energy from being absorbed the first intrinsic layer can be absorbed by the second intrinsic layer. Result The a-Si: H p-i-n and p-i1-i2-n solar cells were characterized including optical properties, electrical properties, surface morphology, thickness, band-gap using Ellipsometric Spectroscopy (ES). Furthermore, from the optical constant and thin film thickness, the reflectance and transmittance of each sample were obtained. The p-i-n and p-i1-i2-n samples show good transparency in the infrared region and this transparency decreases in the visible light region shows an interference pattern with a sharp decrease in transmission at the absorption edge and the performance of solar cells (curve I-V) measured by use sun simulator and sunshine. Conclussion: Our results show that there is a very good increase in the efficiency of the a-Si: H p-i1-i2-n solar cells by 58.6% of the original p-i-n structure.

Mathematical modeling of antireflection coating based on double negative index materials

New artificial Negative index materials (NIMs) or metamaterials have rapidly attracted researchers and industry due to their unusual properties. Applications of various NIMs have been found to be used in manufacturing and design some nano devices such as optical sensors and solar cells. The concept of solar cells depends on the maximizing the light transmission and minimizing the reflection. We propose solar cell structure model based on NIMs to enhance the light efficiency in solar cells. The proposed structure consists of four layers including two NIMs layers called Double NIMs. The simulation of the proposed model has been done utilizing the Transfer Matrix Method (TMM). High transmission and low reflection have been obtained. Solar cells based on double NIMs show promising future and could successfully be used to design highly efficient solar cells.

Stabilization of the J-V Characteristic of a Perovskite Solar Cell Using an Intelligent Control Loop

The phenomena related to charge trapping are among the most relevant open issues that affect the long-term stability of perovskite-based devices. According to this, the objective of this paper is to report experimental results in which a charge control strategy is used for the first time in a solar cell structure that has a high trap density perovskite absorber. This device has also noticeable J-V hysteresis, produced by non-capacitive effects. The control strategy proposed, based on sigma-delta modulation, applies to the device an appropriate sequence of voltage waveforms determined after periodical current measurements made at a constant voltage. The experimental results obtained and the fittings made with a phenomenological model indicate that this approach allows controlling several charge-related effects. As a consequence, the J-V characteristic of the device is successfully shifted and stabilized to predetermined positions.