Superlattices and Microstructures最新文献

Molybdenum trioxide (MoO₃) thin films with thicknesses 300, 400 and 500 nm were deposited on an FTO substrate by thermal evaporation method. The prepared thin films showed both thermochromic and photocatalytic dye degradation properties. The thermochromic property of the prepared thin films was induced by exposing the thin films to argon gas at a temperature varying from 100 °C to 300 °C (in steps of 50 °C). The photocatalytic dye degradation ability of the films were examined by the photodegradation of methylene blue (MB) dye solution under visible light irradiation. MoO₃ thin film with 300 nm thickness is seen to have good thermochromic and photocatalytic dye degradation ability and both of these properties are necessary for smart window applications.

As we all know, the normally-off HEMT is very important to the safety of power electronic systems. To increase the threshold voltage of the device, this article proposes to cover Al₂O₃ on the recessed P-GaN to form the recessed p-GaN HEMT covered with Al₂O₃. Through simulation calculation, covering Al₂O₃ on P-GaN can effectively increase the threshold voltage, but the saturation current and transconductance will be severely reduced. Therefore, this article optimizes the structure and proposes a composite recessed-gate HEMT for the first time. It can obtain high saturation current and high transconductance while maintaining a high threshold voltage. Compared with the recessed p-GaN HEMT covered with Al₂O₃, the transconductance and saturation current of the composite recessed-gate HEMT are increased by 13.14% and 121.33%, respectively, while the threshold voltage is only reduced by 4.44% (4.3 V). In addition, the gate dielectric has a greater impact on device performance. Therefore, this paper analyzes the influence of the thickness of the Al₂O₃ layer on the device through theoretical calculations and obtains the optimal value of the thickness. (T1 = 18.3 nm, Vth = 4.5 V, Isat = 456 mA/mm). The results show that the composite recessed gate has broad application prospects in the next generation of normally-off power device applications.

We present a numerical simulation based study of single graded Cu(In,Ga)Se₂ (Copper Indium Gallium Diselenide) thin film solar cell. In this work, initially a basic CIGS single graded cell structure is optimized in terms of thickness, band-gap and doping concentration. CdS is kept as the buffer layer, which is widely used for high efficiency CIGS solar cells. In the next step, CdS is replaced with ZnMgO as the buffer layer in order to exploit its greater photon absorption ability due to its higher band-gap which further enhances the cell efficiency. A thorough analysis is carried out on the solar cell parameters open circuit voltage (V_oc), short circuit current density (J_sc), fill factor (FF) and quantum efficiency (η) of the photovoltaic cell structure. An intermediate layer of p-type MoS₂ is inserted in between the single graded CIGS absorber layers. The objective is to limit the unintentional Ga inter diffusion and maintain the desired grading during the high temperature annealing for the absorber preparation. The power conversion efficiency of the bilayer device structure with Ga fraction x=(0.31) of the top absorber layer along with Ga fraction y=(0.25) of the bottom absorber layer exhibits an improved efficiency from 24.02% (CdS as the buffer layer) to 25.37% (ZnMgO as buffer layer). An excellent power efficiency of η = 26.78% is reported after adding the intermediate layer of p-type MoS₂ and optimizing its thickness and the carrier concentration.