高色纯度有机白光电致发光器件

介绍了具有高色纯度的多层有机白光器件,器件发光的色坐标为x=0．33,y=0．34,非常接近白光等能点,是色度很好的白光器件。而且在8～14V很大的范围内,发光色度随器件的驱动电压或电流的变化不大,基本稳定在x=0．33,y=0．34。在电压为19V时,器件的亮度达到了最大9735cd／m^2,在电压为9V时,器件的效率达到了最大4．5cd／A。     

一种白光有机电致发光器件的制备

通过对器件结构的优化设计，提高了白光电致发光器件中蓝光成分的发光效率，从而得到了一种较为理想的有机白光电致发光器件。驱动电压为5V时，电流密度J=0．5mA／cm^2，器件的效率达到最大，流明效率为1．92 lm／W，此时器件的发光亮度接近20cd／m^2。色坐标为(x=O．317，y=0．328)。非常接近白光等能点．是色度很好的白光。并且在很大范围内，色度随器件的驱动电压或电流变化不大，当驱动电压变化至15V时。f=232mA／cm^2，色坐标变化至(x=0．338，y=O．353)。在电压为22V时，器件的亮度达到最大，为17 000cd／m^2。此外器件结构相对简单。器件制备的可重复性得到很大程度的改善。     

TBPe作蓝光材料的双层白色有机电致发光器件的性能

选用一种新型高效的蓝光有机小分子荧光染料TBPe,首次制备了以PVK:TBPe为蓝光发光层和Alq₃:rubrene为橙红光发光层的双层白光有机电致发光器件,器件结构为ITO/PVK:TBPe/Alq₃:rubrene/Mg:Ag。通过适当调节各有机层的掺杂比例和厚度,得到了发光性能比较理想的白光器件。器件在7V左右启亮,而且随着外加电压的变化,色坐标基本保持不变,在外加驱动电压为16V时,器件的亮度为738cd/m²,外量子效率为0.2%。我们还尝试选用本身可以发绿白光,而且兼具电子传输特性的母体材料Zn(BTZ)₂替代Alq₃,器件的最大亮度提高到1300cd/m²,色坐标为(0.32,0.36),更加接近白色等能点,器件其他光电性能也得到了显著地提高。     

蓝色发光材料DPVBi掺杂DCJTB发光性质的研究

对蓝光材料DPVBi掺杂红光染料DCJTB的发光性质进行了研究。首先研究了DPVBi掺杂不同质量浓度DCJTB的光致发光，当掺杂质量浓度为0.1％时，光致发光得到白光(色度x=0．36，y=0．34)。基于光致发光的实验结果，以DPVBi掺杂不同质量浓度DCJTB作发光层，制备了结构为ITO／CuPc／NPB／DPVBi：DCJTB/Alq3／LiF／Al的器件，当掺杂质量浓度为0．08％时器件实现了白色发光(色度为x=0．25，y=0．32)。研究了该白光器件的电致发光性质，白光器件在14V时达到最高亮度7822cd／m^2。在20mA／cm^2电流密度驱动下的亮度为489cd/m^2，最大流明效率为1．75lm／W。     

不同电极对蓝光有机电致发光器件性能的影响

利用高真空多源型有机分子沉积系统分别制备了不同负电极为Al、LiF/Al和Mg:Ag的有机小分子多层电致发光器件,比较了不同负极对以五苯基环戊二烯（PPCP）为发光层的蓝光有机电致发光器件性能的影响,发现以LiF/Al作负极的器件在综合性能上优于其它器件。其中器件ITO／TPD／PPDP／Alq/LiF/Al蓝光发射的最大发光亮度达2375cd/m^2,最大发光效率为0.26lm/W.     

柔性衬底白色有机电致发光器件的制备及其性能

采用以ITO为导电层的柔性透明PET基片作为衬底,以2-(2-羟基苯基)苯并噻唑螯合锌(Zn(BTZ),)作为发光层制备出结构为PET／ITO／PVK：TPD／Zn(BTZ)2／Al明亮的近白色柔性有机小分子电致发光器件。发光的色坐标值为x=0．242,y=0．359,在25V的直流电压驱动下,亮度为1000cd／m^2,量子效率达到了0．30％。并进一步在Zn(BTZ)2中掺入橙红色染料Rubrene,制成PET／ITO／PVK：TPD／Zn(BTZ)2：Rubrene／Al结构器件。实现了纯白色发光(色坐标值：x=0．339,y=0．339),非常接近于白色等能点,驱动电压为25V时器件的亮度达1200cd／m^2,且量子效率达0．35％。最后对器件的发光性能及机理进行了深入的研究和探讨。     

DPVBi为激子阻挡层的亚单层有机发光器件的制备与光电性能研究

结合亚单层的有机发光技术,制备了一种多层有机电致发光器件,其结构为ITO/m-MTDATA (50nm)/ C545T (0.05nm) /DPVBi (d nm)/DCM2(0.05nm)/ Alq (60nm) /LiF(1nm) /Al.荧光材料C545T和DCM2以亚单层的方式插入DPVBi前后,通过改变DPVBi的厚度,观察器件性能的变化,当DPVBi为4 nm时,器件在4V电压下最大发光效率是4.19 cd/A,在13 V电压下最大亮度是17050 cd/m2.分析对比了四种不同厚度器件的电流密度-电压曲线、亮度-电压曲线、电致发光光谱图和色坐标,发现选择合适厚度的激子阻挡层,可以得到效率较高的器件.激子阻挡层一般选择载流子传输能力较差,HOMO能级较低的材料.所得结果对有机发光器件尤其是采用亚单层有机白光器件的设计和制作有一定的指导作用.     

一种基于蓝色荧光与磷光敏化技术的高显色指数白光有机电致发光器件的制备

通过采用4,4'-bis(9-ethyl-3-carbazovinylene)-1,1'-biphenyl (BCzVBi)为蓝色荧光发光单元,绿色磷光材料fac tris(2-phenylpyridine) iridium 敏化红色荧光材料4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran (DCJTB)为混合黄色发光单元,制备了一组白光有机电致发光器件。通过对染料掺杂浓度的优化,以及引入适当厚度的4,4-N,N-dicarbazole-biphenyl (CBP)作为中间层,获得了高效率、高显色指数的白光有机电致发光器件。器件在100 cd/m²亮度下的最高显色指数达到了90,此时的色坐标为(0.32,0.32), 非常接近白光等能点。该组器件的最大电流效率达到了11.00 cd/A,相应器件的最大亮度为13 330 cd/m²。     

基于溶液加工小分子材料发光层的有机-无机复合发光器件

报道了基于溶液加工有机小分子材料发光层、聚乙烯亚胺电子注入层的有机-无机复合发光器件. 优化了空穴传输层和磷光染料的掺杂浓度, 得到最佳发光效率的器件. 蓝光、黄光和红光器件的最大外量子效率为17.3%, 10.7% 和7.3%. 在发光亮度为1000 cd/m² 时, 蓝光、黄光和红光器件的外量子效率分别为17.0%, 10.6% 和5.8%, 器件效率下降较小. 原因在于同时采用空穴传输型和电子传输型的小分子材料作为共同主体材料, 器件具有较宽的载流子复合区域, 降低了三线激发态-三线激发态湮灭和三线激发态-极化子相互作用对器件发光效率的影响. 白光器件在亮度为1000 cd/m²时, 发光效率和功率效率为31 cd/A和 14.8 lm/W. 器件的色度为(0.32, 0.42), 色度比较稳定, 随电流的变化微小. 器件的效率较以往报道的有机-无机复合发光器件有显著的提高, 主要归因于在聚乙烯亚胺上能够制备特性良好的小分子材料薄膜, 以及小分子主体材料拥有较高的三线态能量和平衡的载流子传输特性, 能够获得高效的磷光发射.     

TBVB用作蓝光发光层的非掺杂有机电致蓝光和白光器件

利用一种来源于PPV的发蓝光的齐聚物材料2,5,2',5'-tetra(4'-biphenylenevinyl)-biphenyl(TBVB)制作非掺杂的有机电致蓝光和白光器件。蓝光器件的结构为ITO/NPB/TBVB/Alq₃/LiF/Al,其中TBVB用作发光层;白光器件的结构为ITO/NPB/TBVB/rubrene/Alq₃/LiF/Al,其中TBVB与超薄层(平均“厚度”0.05~0.20nm)的Rubrene相结合用作发光层,二者分别发蓝光和黄光。在蓝光器件中,当TBVB的厚度为30nm时,器件发出色坐标为(0.20,0.26)的蓝光,其最大亮度和效率分别达到2154cd/m²和1.62cd/A。在白光器件中,可通过调节TBVB和Rubrene的厚度实现对器件发光色度的调节。当TBVB和Rubrene的厚度分别为10,0.15nm时,器件在亮度为4000cd/m²时发光色坐标为(0.33,0.34),非常接近白光等能点,且随着电压的变化始终处于白光区。当电压为16V时该器件达到最高亮度4025cd/m²;当电压为6V时器件有最高的效率3.2cd/A。     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.