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Efficiency enhancement of InGaN based blue light emitting diodes with InGaN/GaN multilayer barriers 下载免费PDF全文
The advantages of InGaN based light-emitting diodes with InGaN/GaN multilayer barriers are studied.It is found that the structure with InGaN/GaN multilayer barriers shows improved light output power,lower current leakage,and less efficiency droop over its conventional InGaN/GaN counterparts.Based on the numerical simulation and analysis,these improvements on the electrical and the optical characteristics are mainly attributed to the alleviation of the electrostatic field in the quantum wells(QWs) when the InGaN/GaN multilayer barriers are used. 相似文献
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Efficiency and droop improvement in a blue InGaN-based light emitting diode with a p-InGaN layer inserted in the GaN barriers 下载免费PDF全文
The advantages of a blue InGaN-based light-emitting diode with a p-InGaN layer inserted in the GaN barriers is studied. The carrier concentration in the quantum well, radiative recombination rate in the active region, output power, and internal quantum efficiency are investigated. The simulation results show that the InGaN-based light-emitting diode with a p-InGaN layer inserted in the barriers has better performance over its conventional counterpart and the light emitting diode with p-GaN inserted in the barriers. The improvement is due to enhanced Mg acceptor activation and enhanced hole injection into the quantum wells. 相似文献
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随着人们环保意识的不断增强,社会对清洁能源的需求也日益增加.燃料电池具有效率高,燃料来源丰富,可直接将化学能转化成电能且污染小等优点,因而受到了广泛关注.然而,燃料电池的阴极氧还原反应(ORR)速率较慢,成为提高燃料电池整体效率的制约因素.因此,开发高性能的ORR催化剂,加快ORR反应速率具有非常重要的意义.目前,Pt基催化剂被认为是活性最好的商用ORR电催化剂.尽管此类催化剂具有较高的催化活性和良好的稳定性,但Pt的储量有限,价格高昂,抗燃料毒化性能差,限制了其大规模应用.近年来,为了减小Pt的用量,降低催化剂成本,人们除了致力于研究贵金属合金催化剂及非贵金属催化剂外,还把目光聚焦在了非金属催化剂,特别是碳及其复合材料的研究上.在众多碳材料中,碳球因具有良好的表面渗透性和较高的机械稳定性而被广泛应用于催化、吸附、药物输送和能量存储及转化等领域中.然而,碳球的表面化学惰性较强,比表面积较低,使其部分应用受到了限制.因此,人们采用了多种方法来调控碳球的物理化学性质.其中,向碳材料中掺入杂原子,尤其是氮原子的方法广受青睐.因为杂原子的掺入会显著增强作为主体的碳原子给电子的能力和表面吸附性质,从而对ORR表现出优异的催化活性和稳定性.本文以蔗糖作为碳源,三聚氰胺作为氮源,采用水热法及高温热解法制备了一系列氮掺杂的生物质碳球.并对氮掺杂量及热解温度进行了优化.结果表明,石墨化程度及石墨氮含量的提高,能有效地提高催化剂的活性.在优化了的条件下得到的催化剂N0.1C1.9S-900,表现出了比商业Pt/C催化剂更好的ORR催化性能.在0.1 mol/L KOH中,该催化剂催化ORR的起始电位和半波电位分别为–22.6和–133.6 mV(vs.Ag/AgCl),极限电流密度为4.6 mA/cm~2,分别比商业Pt/C高出7.2 mV,5.9 mV和0.2 mA/cm~2.同时,在经过30000 s的稳定性测试中,N0.1C1.9S-900催化剂的电流损失也远低于Pt/C,表明该催化剂具有良好的稳定性.此外,在抗甲醇毒化实验中,相比于商业Pt/C,N0.1C1.9S-900催化剂对甲醇有更好的耐受性.另外,该催化剂催化的ORR属于高效的4e~–途径.可见,该催化剂作为燃料电池的阴极氧还原反应催化剂具有广阔的前景. 相似文献
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Advantages of InGaN/GaN multiple quantum well solar cells with stepped-thickness quantum wells 下载免费PDF全文
InGaN/GaN multiple quantum well (MQW) solar cells with stepped-thickness quantum wells (SQW) are designed and grown by metal-organic chemical vapor deposition. The stepped-thickness quantum wells structure, in which the well thickness becomes smaller and smaller along the growth direction, reveals better crystalline quality and better spectral overlap with the solar spectrum. Consequently, the short-circuit current density (Jsc) and conversion efficiency of the solar cell are enhanced by 27.12% and 56.41% compared with the conventional structure under illumination of AM1.5G (100 mW/cm2). In addition, approaches to further promote the performance of InGaN/GaN multiple quantum well solar cells are discussed and presented. 相似文献
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Enhanced performances of InGaN/GaN-based blue light-emitting diode with InGaN/AIInGaN superlattice electron blocking layer 下载免费PDF全文
InGaN/AIlnGaN superlattice (SL) is designed as the electron blocking layer (EBL) of an InGaN/GaN-based light- emitting diode (LED). The energy band structure, polarization field at the last-GaN-barrier/EBL interface, carrier concen- tration, radiative recombination rate, electron leakage, internal quantum efficiency (IQE), current-voltage (l-V) perfor- mance curve, light output-current (L-l) characteristic, and spontaneous emission spectrum are systematically numerically investigated using APSYS simulation software. It is found that the fabricated LED with InGaN/AIInGaN SL EBL exhibits higher light output power, low forward voltage, and low current leakage compared with those of its counterparts. Meanwhile, the efficiency droop can be effectively mitigated. These improvements are mainly attributed to the higher hole injection efficiency and better electron confinement when InGaN/AIlnGaN SL EBL is used. 相似文献
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Enhanced performance of InGaN/GaN multiple quantum well solar cells with double indium content 下载免费PDF全文
The performance of a multiple quantum well (MQW) InGaN solar cell with double indium content is investigated. It is found that the adoption of a double indium structure can effectively broaden the spectral response of the external quantum efficiencies and optimize the overall performance of the solar cell. Under AM1.5G illumination, the short-circuit current density (Jsc) and conversion efficiency of the solar cell are enhanced by 65% and 13% compared with those of a normal single-indium-content MQW solar cell. These improvements are mainly attributed to the expansion of the absorption spectrum and better extraction efficiency of the photon-generated carriers induced by higher polarization. 相似文献