New Architecture towards Ultrathin CdTe Solar Cells for High Conversion Efficiency

Solar Cell Capacitance Simulator in 1 Dimension (SCAPS-1D) is used to investigate the possibility of realizing ultrathin CdTe based solar cells with high and stable conversion efficiency. In the first step, we modified the conventional cell structure by substituting the CdS window layer with a CdS:O film having a wide band gap ranging from 2.42 to 3.17 eV. Thereafter, we simulated the quantum efficiency, as well as the parameters of J-V characteristics, and showed how the thickness of CdS:O layer influences output parameters of Glass/SnO2/ZTO/CdS:O/CdTe1-xSx/CdTe/Ni reference cell. High conversion efficiency of 17.30% has been found using CdTe1-xSx (x=0.12) and CdTe layers of thickness 15 nm and 4 μm, respectively. Secondly, we introduced a BSR layer between the absorber layer and back metal contact, which led to Glass/SnO2/ZTO/CdS:O/CdTe1-xSx/CdTe/BSR/Ni configuration. We found that a few nanometers (about 5 nm) of CdTe1-xSx layer is sufficient to obtain high conversion efficiency. For BSR layer, different materials with large band gap, such as ZnTe, Cu2Te, and p+-CdTe, have been used in order to reduce minority carrier recombination at the back contact. When ZnTe is used, high conversion efficiency of 21.65% and better stability are obtained, compared to other BSR

Numerical Investigations and Analysis of Cu 2

This paper reports numerical investigation, using SCAPS-1D program, of the influence of Cu2ZnSnS4 (the so-called CZTS) material features such as thickness, holes, and defects densities on the performances of ZnO:Al/i-ZnO/CdS/CZTS/Mo solar cells structure. We found that the electrical parameters are seriously affected, when the absorber thickness is lower than 600 nm, mainly due to recombination at CZTS/Molybdenum interface that causes the short-circuit current density loss of 3.6 mA/cm2. An additional source of recombination, inside the absorber layer, affects the short-circuit current density and produces a loss of about 2.1 mA/cm2 above this range of absorber thickness. The J-V characteristic shows that the performance of the device is also limited by a double diode behavior. This effect is reduced when the absorber layer is skinny. Our investigations showed that, for solar cells having a CZTS absorber layer of thin thickness and high-quality materials (defects density ~1015 cm−3), doping less than 1016 cm−3 is especially beneficial. Such CZTS based solar cell devices could lead to conversion efficiencies higher than 15% and to improvement of about 100 mV on the open-circuit voltage value. Our results are in conformity with experimental reports existing in the literature

Numerical Design of Ultrathin Hydrogenated Amorphous Silicon-Based Solar Cell

Numerical modelling is used to confirm experimental and theoretical work. The aim of this work is to present how to simulate ultrathin hydrogenated amorphous silicon- (a-Si:H-) based solar cells with a ITO BRL in their architectures. The results obtained in this study come from SCAPS-1D software. In the first step, the comparison between the J-V characteristics of simulation and experiment of the ultrathin a-Si:H-based solar cell is in agreement. Secondly, to explore the impact of certain properties of the solar cell, investigations focus on the study of the influence of the intrinsic layer and the buffer layer/absorber interface on the electrical parameters (JSC, VOC, FF, and η). The increase of the intrinsic layer thickness improves performance, while the bulk defect density of the intrinsic layer and the surface defect density of the buffer layer/i-(a-Si:H) interface, respectively, in the ranges [109 cm-3, 1015 cm-3] and [1010 cm-2, 5×1013 cm-2], do not affect the performance of the ultrathin a-Si:H-based solar cell. Analysis also shows that with approximately 1 μm thickness of the intrinsic layer, the optimum conversion efficiency is 12.71% (JSC=18.95 mA·cm−2, VOC=0.973 V, and FF=68.95%). This work presents a contribution to improving the performance of a-Si-based solar cells

Computational Studies on the Molecule 1-(2-Hydroxyethyl)-5-Fluorouracil in Gas Phase and Aqueous Solution and Prediction of Its Confinement inside Capped Nanotubes

Density functional theory (DFT) calculations were performed on a fluorouracil derivative at the B3LYP/6−31+G(d) level. Furthermore, the ONIOM method was performed to investigate the possibility of its confinement inside capped nanotubes. The results found of the structural parameters of the optimized molecule are in good agreement with experimental data. The analysis of thermodynamic properties leads us to predict that the confinement of the studied molecule inside capped nanotubes SWCNT(12,0), SWCNT(14,0), and SWCNT(16,0) is possible. The large Eg values found suggest a good stability for the studied molecule. The predicted nonlinear optical (NLO) properties of the studied molecule are much greater than those of urea. Thereby, it is a good candidate as second-order NLO material. The calculated ∆Gsol values suggest that the studied molecule is more soluble than the 5-FU molecule. The results of quantum molecular descriptors show that the studied molecule is hard electrophile and strongly reactive