Zn doping of InP, InAsP/InP, and InAsP/InGaAs heterostructures through metalorganic vapor phase diffusion (MOVPD)

Zinc incorporation by post-growth metalorganic vapor phase diffusion (MOVPD) is used to achieve high p-doping, which is desirable for the fabrication of photodiodes. Diethylzinc (DEZ) is used as precursor and Zn is diffused into InP and InAs_0.6P epitaxial layers grown by low pressure metalorganic vapor phase epitaxy (MOVPE) on different substrate orientations, enabling the investigation of the dislocation density on the Zn incorporation. Diffusion depths are measured using cleave-and-stain techniques, resistivity measurements, electrochemical profiling, and secondary ion mass spectroscopy. High hole concentrations of, respectively, 1.7 10¹⁹ and 6 10¹⁸ cm⁻³, are obtained for, respectively, InAs_0.60P and InP. The diffusion coefficients are derived and the Zn diffusion is used for the fabrication of lattice-mismatched planar PIN InAsP/InGaAs photodiodes.     

Effects of incorporating salts with various alkyl chain lengths on carrier balance of light-emitting electrochemical cells

Recently, solid-state light-emitting electrochemical cells (LECs) have attracted much attention since they have advantages such as low operation voltages, simple device structure and balanced carrier injection. Salts are commonly added in the emissive layer of LECs to provide additional mobile ions and thus to accelerate device response. However, in addition to modified ionic property, carrier balance of LECs would also be tailored by salt additives. In this work, we improve device efficiency of LECs by incorporating imidazole-based salts bearing various alkyl chain lengths. As the alkyl chain length of the added salt increases, the device current decreases and the recombination zone approaches the anode. These results reveal that hole transport in the emissive layer of LEC containing a salt with a larger size would be impeded more significantly than electron transport. When doped with a salt possessing a proper size, nearly doubled device efficiency as compared to that of the neat-film device can be obtained due to improved carrier balance. This work demonstrates a feasible strategy to improve device performance of LECs and clarifies the physical insights of the effect of salt size on carrier balance of LECs.     

基于载波聚合的下行调度研究

现有LTE-A系统中,由于接入载波能力的差异,LTE用户的性能往往得不到保证。针对这一问题,提出了一种新的联合载波调度的资源分配方案,该方案根据用户类型划分UE所能接入的载波资源组,在后向兼容载波较为紧张时,使LTE-A用户以更大的概率接入到非后向兼容载波,从而保证LTE用户的性能。同时,该方案引入载波选择权重的计算,作为改进的比例公平(Proportional Fair,PF)算法的一个因子,能够实时保证载波间的负载均衡,提升系统吞吐量。     

Efficient inverted polymer solar cells incorporating doped organic electron transporting layer

An efficient inverted polymer solar cell is enabled by incorporating an n-type doped wide-gap organic electron transporting layer (ETL) between the indium tin oxide cathode and the photoactive layer for electron extraction. The ETL is formed by a thermal-deposited cesium carbonate-doped 4,7-diphenyl-1,10-phenanthroline (Cs₂CO₃:BPhen) layer. The cell response parameters critically depended on the doping concentration and film thickness of the Cs₂CO₃:BPhen ETL. Inverted polymer solar cell with an optimized Cs₂CO₃:BPhen ETL exhibits a power conversion efficiency of 4.12% as compared to 1.34% for the device with a pristine BPhen ETL. The enhanced performance in the inverted device is associated with the favorable energy level alignment between Cs₂CO₃:BPhen and the electron-acceptor material, as well as increased conductivity in the doped organic ETL for electron extraction. The method reported here provides a facile approach to optimize the performance of inverted polymer solar cells in terms of easy control of film morphology, chemical composition, conductivity at low processing temperature, as well as compatibility with fabrication on flexible substrates.     

The characteristics of Zn-doped InP using spin-on dopant as a diffusion source

Zn diffusion into InP was carried out ex-situ using a spin-on dopant as a diffusion source. The characteristics of Zn-doped InP are analyzed using low-temperature photoluminescence (PL), differential Hall measurement, and secondary ion mass spectrometry (SIMS). Dopant activation of Zn is close to 100% using this method. Band-to-acceptor (B-A) transition peak is dominant in PL, which is a characteristic usually found in in-situ doping. This evidence along with an activation energy of 0.5 eV show that the diffusion is substitutional rather than interstitial.     

有机缓冲层(Alq3和PBD)和无机缓冲层(TiO2)对OLEDs的不同影响

制备了三种不同缓冲层材料(TiO2、Alq3和PBD)修饰ITO的有机电致发光器件,同没有缓冲层修饰的器件相比,亮度和效率都有很大改善.同时通过比较有缓冲层修饰的三个器件的启亮电压和器件的效率,发现TiO2材料修饰的器件的启亮电压最低(为4 V),效率最高,在电流密度为120 mA/cm2情况下电流效率为5 cd/A;Alq3修饰的器件启亮电压次之(为5V),在相同电流密度下电流效率为4.5 cd/A;PBD材料修饰的器件启亮电压最高(为6 V),相同电流密度下电流效率为3 cd/A.因为ITO表面不平整,缓冲层的修饰使ITO表面得到了改善,由于TiO2的最优化厚度比Alq3和PBD的最优化厚度大,所以对于ITO表面的平整作用也就相应的要强.同时,空穴在有机材料和无机材料中的传输过程是不一样的,有机分子间的电荷移动靠的是分子离化,而无机材料中电荷的转移主要靠的是带传导.而且三种材料HOMO能级也不一样,TiO2材料的HOMO能级(7.2 eV)最高.因此,三个材料中TiO2对于空穴的阻挡作用最大,通过隧穿作用穿过缓冲层材料PBD的空穴数就小于缓冲层材料Alq3和PBD,TiO2修饰的器件的载流子的平衡程度就高于Alq3和PBD修饰的器件,从而效率也相应的高于Alq3和PBD修饰的器件.     

Cu掺杂ZnO薄膜的结构及发光特性

采用溶胶-凝胶旋涂法在玻璃衬底上制备了不同Cu掺杂量的ZnO薄膜。用显微镜和X射线衍射(XRD)研究了Cu掺杂对ZnO薄膜形貌和微结构的影响。结果表明,制备得到的ZnO薄膜具有应变小和c轴择优取向。室温下测量了样品Zn1-xCuxO的光致发光(PL)谱,发现所有样品的PL谱中均观察到435nm左右的蓝光发光带,发光带强度与Cu的掺杂量有关;当x=0.06时,Zn1-xCuxO薄膜的PL谱中出现了较强的蓝光发射。分析了掺杂量对发光性能的影响,并对样品的发光机制进行了探讨,推断出蓝光峰来源于电子由导带底到锌空位(VZn)能级的跃迁及锌填隙(Zni)能级到价带顶的跃迁,它们可通过改变Cu的掺杂量予以控制。     

Enhanced carrier balance by organic salt doping in single-layer polymer light-emitting devices

We have showed that the doping of an organic salt into a PVK-based polymer emissive layer could enhance the carrier balance greatly to result in higher luminance and luminous efficiency. It is found out that the salt-doped devices show the similar operating characteristics of frozen-junction light-emitting electrochemical cells (LECs). With the salt doping of 0.6 wt.% and an appropriate salt activation process, the fabricated PVK-based polymer light-emitting diodes (PLEDs) shows the luminous efficiency of 15 cd/A at the highest luminance of 55,000 cd/m² even without an electron-injecting LiF layer. Due to the enhanced carrier balance, the luminous efficiency is found to be maintained from the turn-on voltage to the voltage for the maximum luminance, which means a linear relationship between luminance and current density.     

Inverted polymer solar cells integrated with small molecular electron collection layer

An efficient inverted polymer solar cell (PSC) is reported by integrating a small molecular electron collection layer (ECL) between indium tin oxide (ITO) cathode and the photoactive layer of blended poly(3-hexylthiophene) and [6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM). The ECL is composed of a cesium carbonate-doped tris(8-hydroxyquinolinato) aluminum (Cs₂CO₃:Alq₃) layer. As determined by photoelectron spectroscopy and electrical measurements, the Cs₂CO₃ doping induces suitable energy level alignment at the ITO/Cs₂CO₃:Alq₃/PCBM interface and the increase in bulk conductivity of organic ECL, which are favorable to electron extraction through Cs₂CO₃:Alq₃ to ITO cathode. In addition, optical simulation indicates that the Cs₂CO₃:Alq₃ layer can act as an optical spacer to modulate the region of highest incident light intensity within the photoactive layer, where absorption and charge dissociation are efficient. The inverted PSC with an optimized Cs₂CO₃:Alq₃ ECL exhibits a power conversion efficiency of 4.83%. The method reported here provides a facile approach to achieve high-performance inverted PSCs at low processing temperature.     

Zn离子掺杂CsPbI3量子点及其色转换LED应用（封面文章·特邀）

全无机钙钛矿量子点因其高光致发光量子产率(Photoluminescence Quantum Yield, PLQY)、带隙可调、高色纯度等特性,在宽色域显示上的应用十分广泛,但其表面缺陷与晶格不稳定限制了其进一步应用。通过热注入法将ZnI₂作为掺杂剂成功合成了Zn²⁺掺杂的CsPbI₃量子点(Zn:CsPbI₃量子点)。试验表明,Zn部分取代了Pb,钙钛矿晶格逐渐收缩但晶型保持不变,提高了辐射衰减率,有效消除量子点缺陷态。Zn:CsPbI₃量子点相较于原始CsPbI₃量子点具有更好的相稳定性,PLQY也从56%提升至98%,同时PLQY在10天后仍可保持在80%以上。选用窄发射的Zn:CsPbI₃,CsPbBr₃与CsPbCl₃量子点作为LED颜色转换材料,在国家电视标准委员会(National Television Standards Committee, NTSC)标准下,其色域达到了135.22%,证明了其在直视型LED显示屏或者液晶显示器(Liquid Crystal Display, LCD)背光领域具有潜在应用前景。

     

脉冲激光诱导Zn/InP掺杂过程中温度分布的解析计算

在实验的基础上 ,分析脉冲激光诱导半导体InP掺杂Zn过程 ,利用简化的一维模型 ,在第三类边界条件下 ,给出一种较直观的脉冲激光辐照有限厚双层材料Zn/InP的温度分布解析形式     

TPA-PPV纳米粒子的制备和尺度效应

TPA—PPV是一种优秀的电致发光材料，具有很高的荧光量子产率。介绍了用再沉淀的方法制备粒子尺寸为20～100nm的TPA—PPV纳米粒子。研究发现，当纳米粒子的尺寸从100nm逐渐减小到20nm时，紫外一可见吸收光谱在400nm附近的吸收和荧光发射光谱在500nm附近的发光都向高能端移动，其光谱发生了蓝移。讨论了其光谱尺度效应的机理。研究结果表明其在新型纳米光电子器件中有着广阔的应用前景。     

集成电路中多晶硅薄膜载流子迁移率的实验研究和理论模型

本文系统地研究了多晶硅薄膜载流子迁移率与掺杂浓度的关系,发现不仅如前人所指出的那样,多晶硅载流子迁移率在中等掺杂区有一极小值,而且同时在高掺杂区存在一个极大值.本文将前人提出的杂质分凝模型、晶粒间界陷阱模型和杂质散射机构结合起来,从理论上计算了极大值及其相应的掺杂浓度与晶粒大小、晶粒间界界面态密度的关系,并与实验结果进行了比较.理论模型较好地说明了实验结果.     

Conversion efficiency improvement mechanisms of polymer solar cells by balance electron–hole mobility using blended P3HT:PCBM:pentacene active layer

To improve the power conversion efficiency of polymer solar cells, the blended P3HT:PCBM:pentacene active layer was used to balance hole–electron mobility and roughen surface. Using space-charged-limited current model to analyze the hole-only devices and the electron-only devices, the P3HT:PCBM:pentacene (weight ratio = 1:0.8:0.09) active layer exhibited balance hole–electron mobility. Compared with the power conversion efficiency of 3.46% of the conventional polymer solar cells using P3HT:PCBM (1:0.8) active layer, the power conversion efficiency of 4.42% was obtained. In other words, the power conversion efficiency was improved about 27.5%.