3．CDT高分子OLED材料外部量子效率增倍

英国剑桥显示器科技公司(CDT)日前宣布，在该公司等参加的一项由欧盟提高资金的研究开发项目中，成功地开发出了外部量子效率比过去提高1倍的高分子OLED材料。采用这种高分子材料的OLED元件的外部量子效率为6％。利用红(R)、蓝(B)、绿(G)中效率最低的红色高分子材料，实现了比过去高1倍的外部量子效率。

应用微纳米结构提升LED外部量子效率

LED的量子效率分成内部量子效率及外部量子效率。提升内部量子效率主要与外延片结构有关,提升外部量子效率主要与芯片制程相关。提升内部量子效率是增加电子、空穴对的结合以产生光子,提升外部量子效率是使在LED内的光子更多散射到空气中。在LED结构上制作具有规则性排列的微纳米结构,增加LED光的萃取,以提升LED的外部量子效率。

四氮杂大环化合物在有机电致发光器件中的应用(英文)

合成了四氮杂大环化合物,Tetraazamacrocycliccompound,6,12,19,25 tetramethyl 7,11:20,24 dinitrilo dibenzo［b,m］［1,4,12,15］tetra azacyclo docosine(TMCD).TMCD作为电子传送材料,探讨了它在有机电致发光器件中的应用.制作了结构为:玻璃基板／ITO阳极／NPD／Alq／TMCD／LiF／Al阴极的器件.评价的结果显示:该有机电致发光器件在538nm的绿色发光来源于Alq层.它的最大外部量子效率为0.84%,视感效率为1.30lm／W.最先提出了四氮杂大环化合物做为电子传送材料,可应用于电致发光领域.

Internal quantum efficiency drop induced by the heat generation inside of light emitting diodes (LEDs)

The reasons for low output power of AlGaInP Light Emitting Diodes (LEDs) have been analysed.LEDs with AlGaInP material have high internal but low external quantum efficiency and much heat generated inside especially at a large injected current which would reduce both the internal and external quantum efficiencies.Two kinds of LEDs with the same active region but different window layers have been fabricated.The new window layer composed of textured 0.5 μm GaP and thin Indium-Tin-Oxide film has shown that low external quantum efficiency (EQE) has serious impaction on the internal quantum efficiency (IQE),because the carrier distribution will change with the body temperature increasing due to the heat inside,and the test results have shown the evidence of LEDs with lower output power and bigger wavelength red shift.

Temperature-dependent efficiency droop behaviors of GaN-based green light-emitting diodes

The efficiency droop behaviors of GaN-based green light-emitting diodes (LEDs) are studied as a function of temperature from 300 K to 480 K. The overall quantum efficiency of the green LEDs is found to degrade as temperature increases, which is mainly caused by activation of new non-radiative recombination centers within the LED active layer. Meanwhile, the external quantum efficiency of the green LEDs starts to decrease at low injection current level (<1 A/cm2 ) with a temperature-insensitive peak-efficiency-current. In contrast, the peak-efficiency-current of a control GaN-based blue LED shows continuous up-shift at higher temperatures. Around the onset point of efficiency droop, the electroluminescence spectra of the green LEDs also exhibit a monotonic blue-shift of peak energy and a reduction of full width at half maximum as injection current increases. Carrier delocalization is believed to play an important role in causing the efficiency droop in GaN-based green LEDs.

A Silicon-Based Positive-Intrinsic-Negative Photodetector Double Linear Array on a Thick Intrinsic Epitaxial Layer

没有光扩大系统，在云测量小粒子，大头针光电探测器的一种新类型有 128 个二极管单位的线性数组完全被设计并且认识到。在各个死，有二排光电二极管线数组，并且各划船有 64 根光电二极管。每根光电二极管有 100 m × 的一种尺寸；有单个产量的 100 m，和他们中的每被沟孤立。他们的深度有象取向附生的层的一样的厚度，它被设计是 30 m 保证光子的足够的吸收并且为 p 类型和 n 类型区域的散开离开边缘。察觉者与其波长是 650nm 的激光被测试了，发光是 50mW/cm 2 。完成的光电流是 2 A。因此，当前的 responsivity 是大约 0.4 A/W，并且外部量效率是 76.45% 。黑暗水流是不到 600 pA。两个都，光子和低黑暗的足够的吸收，电流被利用厚取向附生的内在的层完成。邻近的光电二极管的低干扰被沟也在光电二极管附近保证。与获得的表演，光电探测器能被用来在云测量降水粒子的直径。因此，降雨能基于粒子的直径被判定。

Status of GaN-based green light-emitting diodes

GaN-based blue light emitting diodes(LEDs) have undergone great development in recent years,but the improvement of green LEDs is still in progress.Currently,the external quantum efficiency(EQE) of GaN-based green LEDs is typically30%,which is much lower than that of top-level blue LEDs.The current challenge with regard to GaN-based green LEDs is to grow a high quality In GaN quantum well(QW) with low strain.Many techniques of improving efficiency are discussed,such as inserting Al GaN between the QW and the barrier,employing prestrained layers beneath the QW and growing semipolar QW.The recent progress of GaN-based green LEDs on Si substrate is also reported:high efficiency,high power green LEDs on Si substrate with 45.2% IQE at 35 A/cm2,and the relevant techniques are detailed.

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 (J sc ) 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.

Pure blue and white light electroluminescence in a multilayer organic light-emitting diode using a new blue emitter

We characterized the 6,12-bis{[N-(3,4-dimethylphenyl)-N-(2,4,5-trimethylphenyl)]amino} chrysene(BmPAC),which has been proven to be a blue fluorescent emission with high EL efficiency. The blue fluorescent device exhibits good performance with an external quantum efficiency of 5.8% and current efficiency of 8.9 cd/A, respectively. Using BmPAC, we also demonstrate a hybrid phosphorescence/fluorescence white organic light-emitting device(WOLED) with high efficiency of 36.3 cd/A. In order to improve the relative intensity of blue light, we plus a blue light-emitting layer(BEML) in front of the orange light emitting layer(YEML) to take advantage of the excess singlet excitons. With the new emitting layer of BEML/YEML/BEML, we demonstrate the fluorescence/phosphorescence/fluorescence WOLED exhibits good performance with a current efficiency of 47 cd/A and an enhanced relative intensity of blue light.

Effects of polarization and p-type GaN resistivity on the spectral response of InGaN/GaN multiple quantum well solar cells

Effects of polarization and p-type GaN resistivity on the spectral response of InGaN/GaN multiple quantum well(MQW) solar cells are investigated. It is found that due to the reduction of piezoelectric polarization and the enhancement of tunneling transport of photo-generated carriers in MQWs, the external quantum efficiency(EQE) of the solar cells increases in a low energy spectral range(λ > 370 nm) when the barrier thickness value decreases from 15 nm to 7.5 nm. But the EQE decreases abruptly when the barrier thickness value decreases down to 3.75 nm. The reasons for these experimental results are analyzed. We are aware that the reduction of depletion width in MQW region, caused by the high resistivity of the p-type GaN layer may be the main reason for the abnormally low EQE value at long wavelengths(λ > 370 nm).

Fine-tuning the thicknesses of organic layers to realize high-efficiency and long-lifetime blue organic light-emitting diodes

By using p-bis(p-N,N-diphenyl-aminostyryl)benzene doped 2-tert-butyl-9,10-bis-β-naphthyl)-anthracene as an emitting layer,we fabricate a high-efficiency and long-lifetime blue organic light emitting diode with a maximum external quantum efficiency of 6.19% and a stable lifetime at a high initial current density of 0.0375 A/cm2.We demonstrate that the change in the thicknesses of organic layers affects the operating voltage and luminous efficiency greater than the lifetime.The lifetime being independent of thickness is beneficial in achieving high-quality full-colour display devices and white lighting sources with multi-emitters.

改进光提取的荧光白光OLED器件

本文介绍了外部量子效率为14．5％，光效为31．2流明／瓦的全荧光白光OLED器件。该器件的色座标为（0．387，0．381），完全符合美国能源部能源之星在4000K的室温下的标准要求。当初始亮度为1000cd／m2时，半周期寿命超过了100000d,时。这种高性能是通过改进OLED材料，改善器件的结构以及光提取结构，使得光提取效率提高了2倍以上。

High-efficiency organic light-emitting diodes based on ultrathin blue phosphorescent modification layer

Yellow organic light-emitting devices(YOLEDs) with a novel structure of ITO/MoO_3(5 nm)/NPB(40 nm)/TCTA(15 nm)/CBP:(tbt)_2Ir(acac)(x%)(25 nm)/FIrpic(y nm)/TPBi(35 nm)/Mg:Ag are fabricated. The ultrathin blue phosphorescent bis[(4,6-difluorophenyl)-pyridi-nato-N,C2■](picolinate) iridium(Ⅲ)(FIrpic) layer is regarded as a highperformance modification layer. By adjusting the thickness of FIrpic and the concentration of (tbt)_2Ir(acac), a YOLED achieves a high luminance of 41618 cd/m^2, power efficiency of 49.7 lm/W, current efficiency of 67.3 cd/A, external quantum efficiency(EQE) of 18%, and a low efficiency roll-off at high luminance. The results show that phosphorescent material of FIrpic plays a significant role in improving YOLED performance. The ultrathin FIrpic modification layer blocks excitons in EML. In the meantime, the high triplet energy of FIrpic(2.75 eV) alleviates the exciton energy transport from EML to FIrpic.

Fabrication and characterization of novel high-speed In GaAs/InP uni-traveling-carrier photodetector for high responsivity

A top-illuminated circular mesa uni-traveling-carrier photodetector(UTC-PD) is proposed in this paper. By employing Gaussian graded doping in In Ga As absorption layer and In P depleted layer, the responsivity and high speed response characteristics of the device are optimized simultaneously. The responsivity up to 1.071 A/W(the external quantum efficiency of 86%) is obtained at 1550 nm with a 40-μm diameter device under 10-V reverse bias condition. Meanwhile, the dark current of 7.874 n A and the 3-d B bandwidth of 11 GHz are obtained with the same device at a reverse bias voltage of3 V.

High Efficiency and Stable Organic Light-Emitting Diodes Based on Thermally Activated Delayed Fluorescence Emitter

High efficiency,stable organic light-emitting diodes(OLEDs)based on 2-pheyl-4'-carbazole-9-H-Thioxanthen-9-one-10,10-dioxide(TXO-PhCz)with different doping concentration are constructed.The stability of the encapsulated devices are investigated in detail.The devices with the 10wt% doped TXO-PhCz emitter layer(EML)show the best performance with a current efficiency of 52.1 cd/A,a power efficiency of 32.7lm/W,and an external quantum efficiency(EQE)of 17.7%.The devices based on the 10wt%-doped TXO-PhCz EML show the best operational stability with a half-life time(LT50)of 80 h,which is 8h longer than that of the reference devices based on fac-tris(2-phenylpyridinato)iridium(Ⅲ)(fr(ppy)_3).These indicate excellent stability of TXO-PhCz for redox and oxidation processes under electrical excitation and TXO-PhCz can be potentially used as the emitters for OLEDs with high efficiency and excellent stability.The high-performance device based on TXO-PhCz with high stability can be further improved by the optimization of the encapsulation technology and the development of a new host for TXO-PhCz.

Highly sensitive polymer photodetectors with a wide spectral response range

A series of highly sensitive polymer photodetectors(PPDs) was fabricated with P3HT100-x:PBDT-TS1x:PC71BM1 as the active layers, where x represents the PBDT-TS1 doping weight ratio in donors. The response range of PPDs can cover from the UV to near-infrared regions by adjusting the PBDT-TS1 doping weight ratio. The best external quantum efficiency(EQE) values of ternary PPDs with P3HT:PBDT-TS1:PC_(71)BM(50:50:1 wt/wt/wt) as the active layers reach 830%, 720%,and 330% under 390-, 625-, and 760-nm light illumination and-10 V bias, respectively. The large EQE values indicate that the photodetectors utilise photomultiplication(PM). The working mechanism of PM-type PPDs can be attributed to interfacial trap-assisted hole tunnelling injection from the external circuit under light illumination. The calculated optical field and photogenerated electron volume density in the active layers can well explain the EQE spectral shape as a function of the PBDT-TS1 doping weight ratio in donors.

韩国科学技术院开发出使用石墨烯的有机EL元件

韩国科学技术院（KAIST）开发出以石墨烯替代铟锡氧化物半导体透明导电膜（ITO）作为透明导电膜的绿色发光有机EL元件。该元件主要用于显示器。该发光元件的外部量子效率（EQE）高达40．8％，肉眼感觉的发光效率高达160．31m／W。虽然以往也有用石墨烯作为透明电极的有机EL元件，但这次新开发的元件具有EQE和发光效率都非常高的特点。据研究人员称，发光效率及EQE高的原因是因为有机EL元件设置了共振器结构。因此，提高了特定波长的选择效果，同时也减少了电极上表面等离子体造成的损耗。

Excess Carrier Lifetime Improvement in c-Si Solar Cells by YAG:Ce^(3+)-Yb^(3+)

Ce^(3+)-Yb^(3+) doped Y_3A_(15)O_(12)(YAG) is a luminescent down-conversion material which could convert visible photons to near infrared photons.In this work,YAG:Ce^(3+)-Yb^(3+) is applied on the front surface of mass-produced mono crystalline Si solar cells.For the coated cells,the external quantum efficiency from the visible to the near infrared is improved,and the energy conversion efficiency enhances from 11.70% to 12.2% under AM1.5G.Furthermore,the phosphor down-conversion effect on the solar cell is characterized by the microwave detected photoconductivity technique on the n-type silicon wafer under the 977 nm excitation.The down-conversion materials improve the average excess carrier lifetime from 22.5 μs to 24.2 μs and the average surface recombination velocity reduces from 424.5 cm/s to 371.6 cm/s,which reveal the significant reduction in excess carrier recombination by the phosphors.

“高端应用稀土荧光粉及其规模化制备技术”通过验收

日前,863计划新材料技术领域＂高端应用稀土荧光粉及其规模化制备技术＂课题在西安顺利通过验收。课题通过组成优化和合成条件突破,开发出10余种LED用荧光粉及其规模化制备技术。黄色、红色和绿色荧光粉的外部量子效率分别达到0.9、0.73和0.78,所封装的白光LED光效大于130lm/W。同时开发出5种普通型及宽色域型CCFL用阳光分及其规模化制备技术、5款高效3D．PDP用荧光粉、4种新型测热用稀土发光材料。建成了年产200吨的CCFL荧光粉和年产50吨的LED荧光粉生产线。