Papers by Keyword: Conversion Efficiency

Abstract: Core-shell nanocrystals are utilized to improve vitality conversion efficiency of Si based solar cells. In the present work, a study of synthesis and characterization of photo luminescent, down-shifting, core-shell CdSe/CdS quantum dots is introduced. The QD^,s absorb in the UV range (350nm) of the solar spectrum and emit photons with wavelengths centered at (574 nm). Calculated energy gap is (2.16 eV), which is well suited for Silicon absorption and electron-hole pair generation. The grain size is ranged between (1.814 and 3.456 nm). Results show that the cell efficiency is improved from (8.81%) (For a reference silicon solar cell) to (10.07%) (For a CdSe/CdS QD deposited directly on the surface of the solar cell). This improvement is referred to the spreading of the absorbed solar radiation over the spectral response of the Si solar cell.

Abstract: Carbon nanotubes are one of the materials that can replace platinum as DSSC’s counter electrode. By utilizing carbon nanotubes (CNT), which is an organic material in place of platinum it is possible to create an inexpensive solar cell. However, there are still many problems with CNT such as low conversion compared with platinum and fast degradation in CNT. At the present time, it is to be large surface area when we fabricate CNT electrode sintered at 500°C with Electrophoretic Deposition (EPD). We measured how conversion efficiency changed by changing sintering temperatures. As a result, when CNT electrode sintered at 500°C, conversion efficiency was the highest and it was 2.46%.

Abstract: The thermal management of power module is one of the key important issues for power conversion circuit design. SiC power module is expected to give less conduction and switching loss than conventional Si device, which enables to facilitate the thermal management of a power conversion circuit. This paper develops 2in1 Full-SiC power module and studies the applicability for 600V→300V, 15kW DC-DC buck converter. The feasible thermal design of SiC power module to serve rated operation of the converter circuit is discussed based on the elemental experiments. The developed full-SiC power module realized lower loss and smaller converter circuit than conventional-Si power module.

Abstract: The center of czochralski (CZ) wafer for solar cell often has black center, due to the existence of high impurities content, many defects such as dislocations. This has serious effect on solar cells’ conversion efficiency. To solve this problem, we developed a new kind of material-czochralski and floating zone (CFZ) silicon. But there is still black center in the CFZ-Si wafer with conventional process. In order to solve this problem successfully a new technology-alternant forward and reverse rotation was introduced. By testing the crystal defects, metal and oxygen impurities content, it has been found that the black center is related to oxygen distribution in the wafer. However since the content was very low and not enough to affect the solar cells’ conversion efficiency, which has been testified in solar cell. Therefore CFZ technology offers a new kind of silicon material, which can avoid the black center problem in CZ silicon wafer.

Abstract: Solar energy is an inexhaustible and renewable energy without environmental pollution. Solar energy can be used in three kinds of forms: solar thermal energy, photochemical conversion and photovoltaic power generation. Among these, the final form of photovoltaic power generation is electricity which can be transported, applied and stored conveniently. On the basis of photovoltaic effect, solar cell is developed as a new technology to convert light energy into electrical energy using semiconductor. Up to now the two key problems of the development of solar cells are how to improve the conversion efficiency and reduce cost. Therefore, the material and production technology used for solar cells are discussed based on improving conversion efficiency in this article.

Abstract: This paper presents the design of a compact 2.45 GHz microstrip rectenna for wireless sensors’ power supply. In energy harvesting system, the ambient RF energy can be collected by the rectenna and converted to direct current, therefore, it can be applied to the power supply of low-power wireless sensor. Voltage doubling rectifier circuit and T-type microstrip impedance matching network are applied to this rectenna to increase the output voltage and the rectification efficiency. The antenna is fabricatied ​​by using double PCB board (FR4), and it is optimized by ADS to achieve the best performance. The measurement results show that the rectifier can reach the highest conversion efficiency of 78% when the load resistance is 320 Ω and the input power is 18 dBm. It also greatly improves rectenna’s conversion efficiency at lower input power when the input power is-20 dBm, which has great practical value for supplying low power consumption sensors.

Abstract: A high efficiency rectifying antenna (rectenna) is designed at 5.8 GHz by using defected ground structure (DGS) filters for low-power energy transfer. A slot-coupled patch antenna is used as a receiving antenna with a high gain of 8.2dB. A DGS low-pass filter at the input port of the rectifying circuit is used to suppress the high order harmonics by 20dB. A DGS dc-pass filter is designed to block the AC signal from transmitting to the load. Both of the antenna and the filters are simulated by the full wave EM analysis software of HFSS. The RF-DC conversion efficiency of 51.8% is obtained when the received power is as low as 3mW.

Abstract: In photoelectric micro-power supply integrated on chip, the conversion efficiency of solar cell was lower compared with canonical solar cell. In order to improve the conversion efficiency of the solar cell, three technologies (fabricating back surface field, fabricating surfaces texture and reflector) were adopted in integrated process of photoelectric micro-power supply on chip. The relevant theory of the three technologies was introduced. The optimum schedule of the photoelectric micro-power supply integrated on SOI wafer was proposed. The conversion efficiency of solar cells was analyzed by simulation tools (PC1D). The results prove the conversion efficiency of solar cells was improved from 9. 34% to 13.3%.

Abstract: Optically powered system is a revolutionary new power delivery system, in which optical power is delivered over fiber to photovoltaic power converter, where optical power is transformed into electrical power. Therefore the system is inherently immune to RF, EMI, high voltage and lighting effects. Capable of powering electronic circuitry by optical fiber, this technology has been validated in industries such as electric power, communications, remote sensing and aerospace. To a large extent, photovoltaic power converter is a key component that decides the performance of optically powered system. In this paper, the commonly used GaAs photovoltaic power converter is studied and tested. Parameter values like open circuit voltage, short circuit current, maximum output power, conversion efficiency and the optimum load resistance are obtained through experiment, which can be severed as important reference while choosing or designing DC-DC converter.

Abstract: A composite TiO₂ photoelectrode structure is explored to optimize the dye-sensitized solar cell (DSSC) properties. The composite TiO₂ photoanodes consist of two nanoparticular TiO₂ layers with different size and thickness. The impact of film thickness on the performance of DSSCs was also investigated. In the optimized composite photoelectrode structure with large sized TiO₂ nanoparticle as light scattering layer, the significantly improved performance of DSSC with 25% increase of current density and 13.1% increase of conversion efficiency was experimentally demonstrated.