Advantages of InGaN/GaN multiple quantum well solar cells with stepped-thickness quantum wells

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.     

电磁诱导吸收和透明的可控切换

在一个非简并三能级梯型原子系统中,通过调谐探测场的强度,从理论和实验上研究了探测场通过铷原子蒸气的传输谱线。当探测场不再足够弱时,通过缀饰微扰链的方法推导了探测场响应的表达式并预言了电磁诱导吸收(electromagnetically induced absorption, EIA)的存在。实验上,在室温铷原子的D2线中,当弱探场状态切换到强探测状态时,不局限于单光子共振条件,电磁感应透明(electromagnetically induced transparency, EIT)向EIA的转换在探测场的不同失谐量处被实现。利用缀饰能级图分析了强的探测场和耦合场产生的二级缀饰态之间的相长干涉是EIA形成的主要原因。由于EIT和EIA的许多应用依赖于共振附近的异常色散,这个结果引入了控制色散符号的新能力。     

退火对AlGaInP/GaInP多量子阱 LED外延片性能的影响

采用LP-MOCVD技术在n-GaAs衬底上生长了AlGaInP/GaInP多量子阱红光LED外延片.研究表明退火对外延片性能有重要影响.与未退火样品相比,460℃退火15min,外延片p型GaP层的空穴浓度由5.6×10¹⁸cm^-3增大到6.5×10¹⁸cm^-3,p型AlGaInP层的空穴浓度由6.0×10¹⁷cm^-3增大到1.1×10¹⁸cm^-3.但退火温度为780℃时,p型GaP层和p型AlGaInP层的空穴浓度分别下降至8×10¹⁷cm^-3和1.7×10¹⁷cm^-3,且Mg原子在AlGaInP系材料中的扩散加剧,导致未掺杂AlGaInP/GaInP多量子阱呈现p型电导.在460～700℃退火范围内,并没有使AlGaInP/GaInP多量子阱的发光性能发生明显变化.但退火温度为780℃时,AlGaInP/GaInP多量子阱的发光强度是退火前的2倍.     

Dual-blue light-emitting diode based on strain-compensated InGaN-AlGaN/GaN quantum wells

Strain-compensated InGaN quantum well (QW) active region employing tensile AlGaN barrier is analyzed. Its spectral stability and efficiency droop for dual-blue light-emitting diode (LED) are improved compared with those of the conventional InGaN/GaN QW dual-blue LED based on stacking structure of two In_0.18Ga_0.82N/GaN QWs and two In_0.12Ga_0.88N/GaN QWs on the same sapphire substrate. It is found that the optimal performance is achieved when the Al composition of strain-compensated AlGaN layer is 0.12 in blue QW and 0.21 in blue-violet QW. The improvement performance can be attributed to the strain-compensated InGaN-AlGaN/GaN QW that can provide a better carrier confinement and effectively reduce leakage current.     

石墨烯基纤维电容器的可控制备及应用

超级电容器又名电化学电容器,是一种绿色储能器件。 超级电容器的研究,从根本上讲是寻找比表面积大且可以被充分利用的电极材料。 石墨烯作为sp²杂化碳质材料的基元单位,具有独特的二维结构和优异的物化特性,使得其在超级电容器领域具有巨大的应用潜力,其中石墨烯纤维超级电容器受到了研究工作者越来越广泛的关注。 本文通过对一维石墨烯纤维的自组装以及与制备材料的共组装来作为超级电容器的电极材料,对其可控制备进行了系统的归纳和总结,可控构建独特的电极材料,使其性能得以优化,组装出高性能的超级电容器,并对相关领域的发展趋势做了展望。     

退火对EBE,IBS和ALD沉积HfO2薄膜的抗激光损伤性能影响

结合自身实验条件采用电子束蒸发(EBE)、离子束溅射(IBS)和原子层沉积(ALD)三种工艺制备了HfO2薄膜,对其进行退火实验,采用1064 nm Nd:YAG激光测定了即时沉积和退火后各HfO2薄膜的抗激光损伤能力。研究发现,ALD HfO2薄膜的激光损伤阈值最高,EBE HfO2薄膜次之,IBS HfO2薄膜的损伤阈值最低;300℃退火对各工艺薄膜抗激光损伤能力的影响均为负面,500℃退火则会显著降低ALD HfO2薄膜的抗激光损伤能力。     

3，3’-偶氮-（6-氨基-1，2，4，5-四嗪）的合成与表征

以硝酸胍和水合肼为原料，经7步反应合成了高氮含能化合物3，3＇-偶氮-（6-氨基-1，2，4，5-四嗪），其结构经^1H NMR，^13C NMR，IR及元素分析表征。     

3,3′-偶氮-(6-氨基-1,2,4,5-四嗪)的合成与表征

以硝酸胍和水合肼为原料,经7步反应合成了高氮含能化合物3,3′-偶氮-(6-氨基-1,2,4,5-四嗪),其结构经1H NMR,13C NMR,IR及元素分析表征。     

Electronic structures and optical properties of Ⅲ_A-doped wurtzite Mg_(0.25)Zn_(0.75)O

The energy band structures, density of states, and optical properties of IIIA-doped wurtzite Mg0.25Zn0.75O(IIIA= Al,Ga, In) are investigated by a first-principles method based on the density functional theory. The calculated results show that the optical bandgaps of Mg0.25Zn0.75O:IIIAare larger than those of Mg0.25Zn0.75 O because of the Burstein–Moss effect and the bandgap renormalization effect. The electron effective mass values of Mg0.25Zn0.75O:IIIAare heavier than those of Mg0.25Zn0.75 O, which is in agreement with the previous experimental result. The formation energies of MgZnO:Al and MgZnO:Ga are smaller than that of MgZnO:In, while their optical bandgaps are larger, so MgZnO:Al and MgZnO:Ga are suitable to be fabricated and used as transparent conductive oxide films in the ultra-violet(UV) and deep UV optoelectronic devices.     

测定电池的电动势和内阻

给出了电池电动势和内阻测定的仪器和电路选择，并从多个方面对有关实验误差进行了分析。