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A high-efficiency CdS/CdTe solar cell with step doped absorber layer, optimized back surface field layer, and long carrier lifetime in the absorption layer was designed. At first, The CdS/CdTe reference cell is simulated and compared with previous experimental data. In order to obtain the highest efficiency, the thickness and step doping of the absorber and back surface field layer were optimized. In addition, the effect of carrier lifetime variation in the CdTe layer on the conversion efficiency of CdTe cell was investigated. Compared with reference cell, Efficiency enhancement of the proposed structure was 4.44%. Under global AM 1.5 conditions, the optimized cell structure had an open-circuit voltage of 0.987 V, a short-circuit current density of 27.9 mA/cm 2 and a fill factor of 82.4%, corresponding to a total area conversion efficiency of 22.76%.

This paper presents a radio-frequency (RF) small-signal model for the hetero-gate-dielectric p-n-p-n tunnel field-effect transistor (HG p-n-p-n TFET) that includes the charge conservation capacitance and the substrate parameters. The HG p-n-p-n TFET is evaluated in terms of various RF parameters, including the cut-off frequency, the maximum oscillation frequency, capacitances, resistances, conductances, and transport time delay. The extracted small-signal parameters and RF performance values are compared with those of the low-κ p-n-p-n TFET. A nonquasistatic RF small-signal model has been used along with SPICE simulations and small-signal parameters that were extracted from the simulated device Y-parameters to simulate the HG p-n-p-n TFET. It is confirmed using the Y-parameters and the extracted parameters that this model with the extracted charge conservation capacitance and substrate parameters is valid in the high frequency range up to 100 GHz. In addition, it is shown that a significant circuit performance error may be introduced if the charge conservation capacitance and the substrate parameters are not considered appropriately.

Abstract:In the present work, a new structure of vertical cavity surface emitting laser (VCSEL) is designed and simulated. In this structure, InGaAsP is used as the active region which is sandwiched between GaAs/AlGaAs distributed bragg mirror at the top of structure and GaAs/AlAs distributed bragg mirror at the bottom. In this work, the hole etching depth was continued down to the top of lower spacer layer while in the previous work the hole etching depth was only down to top of the upper spacer. In this way, the threshold current decrement of 76.52% and increment the power by 28% from 5 mW to 6.4 mW at bias current of 9 mA was achieved. In this paper, device characteristics such as light power versus electrical current and voltage versus current are simulated and compared with the previous work. Keywords: design, high power, InGaAsP, VCSEL Classification: Optoelectronics, Lasers and quantum electronics, Ultrafast optics, Silicon photonics, Planar lightwave circuits Amann, "Vertical-cavity surface-emitting laser diodes at 1.55 μm with large output power and high operation temperature," Electron. Lett., vol. 37, pp. 1295Lett., vol. 37, pp. -1296Lett., vol. 37, pp. , 2001 N. Nishiyama, C. Caneau, G. Guryanov, X. S. Liu, M. Hu, and C. E. Zah, "High efficiency long wavelength VCSEL on InP grown by MOCVD," Electron. Lett., vol. 39, pp. 437-439, 2003. [13] A. Karim, J. Piprek, P. Abraham, D. Lofgreen, Y.-J. Chiu, and J. ReferencesE. Bowers, "1.55-um vertical-cavity laser arrays for wavelength-division multiplexing," IEEE

Due to limited availability and the rising price of telluride, the biggest challenge in solar Photovoltaic (PV) is to successfully design and fabricate optimized CdTe solar cells with reducing the cell thickness that show simultaneously high efficiency and current density. A novel structure of ultrathin CdTe solar cells is proposed in this paper that focuses on conversion efficiency. This structure achieved by rotating 90 o in the base line structure that suggests high efficiency due to the high current density. The result showed a considerable improvement over the 15% efficiency of the reference solar cell. The proposed structure is quite noteworthy in reducing the amount of material used and associated losses. Under global air mass (AM) 1.5 conditions, an open-circuit voltage (V oc) of 866 mV, a short-circuit current density (J sc) of 74.84 mA/cm 2 , and a fill factor (FF) of 48.2% were obtained corresponding to a conversion efficiency of 31.2%.