Enhanced performances of InGaN/GaN-based blue light-emitting diode with InGaN/AIInGaN superlattice electron blocking layer

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.     

关于一种开尔文方程推导方法的讨论

不同版次物理化学教材对开尔文方程推导的方法不同。本文通过对吉布斯界面热力学基本方程中球状液滴压强的分析,并依据对于弯曲液滴,附加压力本质上就是由弯曲液面表面张力引起的,得出某物理化学教材中,对小液滴的气液两相平衡过程,其吉布斯自由能的变化为零。对于恒温下,把处于外压为p0的平面液滴分割为处于外压为p_r的小液滴的过程,其吉布斯自由能的变化为2σM/ρr。     

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.     

褐藻硫酸根含量的离子色谱法分析

建立了碱熔-离子色谱测定褐藻中硫酸根含量的方法。样品采用NaOH熔剂,置于马弗炉500℃碱熔45min,经溶解,离心分离,阳离子交换树脂交换后,进样分析。色谱柱为IonPac AS11-HC,以KOH为淋洗液,设置梯度淋洗程序,淋洗液流速为1mL/min。在所选实验条件下,硫酸根在0.4—400mg/L浓度范围内具有良好的线性关系,相关系数r为0.9991,相对标准偏差为2.42%,检出限为0.6mg/kg,回收率在92.17%—109.0%之间。实验证明该方法操作简单,分析快速,结果准确,精密度高,适合于褐藻样品中硫酸根含量的测定。样品分析结果显示褐藻硫酸根含量丰富,尤其是羊栖菜,平均硫酸根含量达40.54g·kg^-1。     

水质砷自动分析仪比对实验方法的探讨

探讨了砷自动分析仪与原子荧光法测定的实验方法,用水样相对误差绝对值的平均值（A值）和t检验两种方法对比对结果进行了判断。找出了9项环境保护行业标准之外的自动分析仪,在实际工作中比较切实可行的比对实验的方法。     

Enhanced performances of InGaN/GaN-based blue light-emitting diode with InGaN/AlInGaN superlattice electron blocking layer

InGaN/AlInGaN superlattice(SL) is designed as the electron blocking layer(EBL) of an InGaN/GaN-based lightemitting diode(LED). The energy band structure, polarization field at the last-GaN-barrier/EBL interface, carrier concentration, radiative recombination rate, electron leakage, internal quantum efficiency(IQE), current–voltage(I–V) performance curve, light output–current(L–I) characteristic, and spontaneous emission spectrum are systematically numerically investigated using APSYS simulation software. It is found that the fabricated LED with InGaN/AlInGaN 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/AlInGaN SL EBL is used.     

Droop improvement in blue InGaN light-emitting diodes with GaN/InGaN superlattice barriers

GaN/InGaN superlattice barriers are used in InGaN-based light-emitting diodes （LEDs）. The electrostatic field in the quantum wells, electron hole wavefunction overlap, carrier concentration, spontaneous emission spectrum, light-current performance curve, and internal quantum efficiency are numerically investigated using the APSYS simulation software. It is found that the structure with GaN/InGaN superlattice barriers shows improved light output power, and lower current leakage and efficiency droop. According to our numerical simulation and analysis, these improvements in the electrical and optical characteristics are mainly attributed to the alleviation of the electrostatic field in the active region.     

Enhanced performance of InGaN/GaN multiple quantum well solar cells with double indium content

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.