有机-无机混合阳离子钙钛矿发光二极管研究进展

 有机-无机杂化钙钛矿具有制备方便、光学带隙可调、电荷传输性能优异等特性,正成为新一代革命性的半导体光电材料。随着研究的不断发展,钙钛矿材料的量子产率已经超过90%。材料合成的快速发展促进了其在光电子器件上的应用,包括太阳能电池、发光二极管、光电探测器和晶体管等。本文回顾了有机-无机混合阳离子钙钛矿发光二极管的最新研究进展,包括材料晶体结构、纳米晶合成过程、器件制备及其光电特性表征。有机-无机混合阳离子为高量子产率钙钛矿纳米晶的合成开辟了一种新的途径,同时也为制备高亮度、高效率发光二极管器件提供了新的思路。     

NPB/Alq_3有机发光二极管的光学模拟

采用偶极子源项和转移矩阵来描述结构内外的光电场分布,并通过Matlab编程,建立了符合有机发光二极管(OLED)实际器件的光学模型。利用该光学模型进行模拟计算具有NPB/Alq3结构的OLED,得到了电致发光(EL)光谱与器件中光出射角之间的关系并结合人眼视觉函数,得到器件亮度与角度的关系,当出射角度逐渐增大时,亮度逐渐减小。另外,制备了不同8-羟基喹啉铝(Alq3)电子传输层厚度的器件,并测量其电致发光光谱,发现模拟计算的理论光谱与测量结果相吻合。并且还发现随着Alq3有机层厚度增加,OLED电致发光光谱的峰位会发生一定的红移。     

Fabrication and spectra characteristics of high efficiency white organic light-emitting diodes with single emitting layer

High-efficiency white organic light-emitting devices with single emitting layer are demonstrated. N,N‘-diphenyI-N,N‘-bis(1,1‘-biphenyl)-4,4‘-diamine (NPB) is used as hole transport layer, while 4,7-diphenyl-l,10-phenan-throline (BPhen) as electron transport layer and 9,10-di-(2-naphthyl)-2-terbutyl-anthracene (TADN) doped with the fluorescent dye 4-(dicyanomethylene)-2-t-buty1-6-(1,1,7,7-tetramethyljulolidyl-9-enyl) (DCJTB) as single emissive layer. The effects of performance by the concentration of DCJTB and the thickness of emissive layer are studied. The device with a structure of indium tin oxide/NPB (50 nm)/TADN: 0.2% DCJTB (15 nm)/BPhen (40 nm)/Mg: Ag shows a maximum brightness of 11400 cd/m^2, a peak current efficiency of 5.6 cd/A and power efficiency of 4.1 Ira/W, while the low turn-on voltage of 3.1 V and the stability of the Commission International De L‘Eclairage coordinate. The spectra through color filter of the device are also studied.     

功率型发光二极管芯片的温度场与应力场

发光二极管(LED)的结点温度和应力分布对它的发光效率、可靠性和寿命有着至关重要的影响。为了优化器件的性能,该文利用有限元方法对功率型LED芯片在不同输入功率、基板材料、换热条件下的温度和热应力进行了模拟与分析。结果表明,目前广泛应用的Sapphire基板效果不是很好,如果能减小晶格不匹配的影响,采用硅基板是较好的选择。当基板导热系数、换热系数大于一定值后,单纯的改进基板的导热系数或强化基板换热,对提高器件的性能已经没有明显的效果。     

功率型发光二极管芯片的温度场与应力场

发光二极管(LED)的结点温度和应力分布对它的发光效率、可靠性和寿命有着至关重要的影响。为了优化器件的性能,该文利用有限元方法对功率型LED芯片在不同输入功率、基板材料、换热条件下的温度和热应力进行了模拟与分析。结果表明,目前广泛应用的Sapphire基板效果不是很好,如果能减小晶格不匹配的影响,采用硅基板是较好的选择。当基板导热系数、换热系数大于一定值后,单纯的改进基板的导热系数或强化基板换热,对提高器件的性能已经没有明显的效果。     

Tunable and enhanced luminescence of Ba2−xCaxSiO4−yN2/3y:Eu2+ phosphors for white light-emitting diodes

Color tuning and luminescence enhancement are predominant challenges for improving the performance of white light emitting diodes(LEDs) toward commercial application. In this paper, a novel promising Ba_(2-x)Ca_xSiO_(4-y)N_(2/3y):Eu~(2+) tphosphors with tunable and enhanced luminescence for phosphors converted LEDs(pc-LEDs) have been successfully synthesized by a direct gas-reduction nitridation method. The effects of Ca and N doping on the phase purity, morphology and optical properties of Ba_(2-x)Ca_xSiO_(4-y)N_(2/3y):Eu~(2+) tphosphors were also systematically investigated. The optical results show that Ba_(2-x)Ca_xSiO_(4-y)N_(2/3y):Eu~(2+) tphosphors can be actively excited over a broad range from 250 to430 nm. With the adding of different concentrations of Ca~(2+) tions in phosphors, the emission color wavelength can be tailored from 501 to 441 nm by a 375 nm NUV LED excitation source. Furthermore, it has been found that the emission and absorption of Ba_(2-x)Ca_xSiO_(4-y)N_(2/3y) tphosphor can be significantly improved when N~(3-) ions were introduced into the host lattices. The intensity of Ba_(1.5)Ca_(0.5)SiO_(4-y)N_(2/3y):Eu~(2+) tphosphor was 3.4 times higher than the phosphor without N doping. The fabrication and characterization of pc-LEDs using Ba_(2-x)Ca_xSiO_(4-y)N_(2/3y):Eu~(2+) tphosphors-silica gel as the coating layer onto 375 nm-emitting In Ga N LED caps demonstrated the superior optical and current tolerant properties,making it a promising and competitive candidate for commercial utilization in white LED applications.     

The spectroscopic properties of Dy3+and Eu3+ co-doped Y3Al5O12 (YAG) phosphors for white LED

Tunable full color emissive Y32.94-xAl5O12: 0.06 Dy3+, xEu3+(YAG: 0.06 Dy, xEu) phosphors with emission peaks at 483 nm(blue), 582 nm(yellow) and 610 nm(red) were synthesized by a sol–gel method. The as-synthesized phosphors were characterized by X-ray powder diffraction(XRD), transmission electron microscopy(TEM), photoluminescence decay lifetimes, photoluminescence excitation and emission spectra. The results showed that photoluminescence intensity varied with excitation wavelength and the doping concentration of Eu3+. The co-doping with Eu3+ compensated the red emission component of the YAG: Dy3+ phosphor. The chromaticity coordinate of YAG: 0.06 Dy, 0.09 Eu phosphor(0.3263, 0.3334) was very close to that of the ideal white light(0.3333, 0.3333). Thus, the YAG: 0.06 Dy, 0.09 Eu phosphor can find potential application in simulating the sunlight artificially through fabricating white light emitters.     

有机电致发光白光器件的研究

白光有机电致发光器件在显示领域有着极大的应用前景,受到人们广泛的关注.通过对白光有机电致发光器件的结构、工作原理、实验的可行性分析、工艺流程、存在的问题等方面进行了分析,对器件结构进行了优化设计,确定了合理的技术路线,提高白光电致发光器件中各成分的发光效率,从而得到了一种较为理想的有机白光电致发光器件.     

Flexible organic light-emitting diodes with ITO／Ag／ITO multi-layers as anodes

The transparent ITO/Ag/ITO multi-layers are developed as anodes on flexible PET (poly(ethylene terephthalate)) substrates. The influence of these anodes on FOLED (Flexible Organic Light-emitting Diodes) is investigated. From the results of research, it can be seen that the multi-layer anode has optimum characteristics, whose sheetresistance is 11 Ω and optical transmittance is about 80%,when the thickness of Ag sandwiched by two ITO layers is in the range of 14--18 nm. It is demonstrated that the OLED devices with multi-layer anodes give better luminescence and higher efficiency compared with those with single ITO anodes.     

单层有机发光二极管中电场与载流子密度的分布

建立了单层 (有机发光二极管 )中载流子注入、输运和复合的理论模型 ,通过求解非线性Painleve方程得到了电场强度随坐标变化的解析函数关系式 ,计算并讨论了载流子迁移率对电场强度、载流子密度等的影响。结果表明 :空间电荷分布不均匀造成了电场强度的不均匀分布。当在器件中占主导地位的载流子具有较低的迁移率或少数载流子具有较高的迁移率时 ,有利于载流子的输运与复合 ,发光性能可得到较大提高。     

量子点层厚度对量子点发光二极管发光特性的影响简

采用湿法旋涂技术制备量子点发光二极管器件（QD-LEDs）。PEDOT作为空穴注入层,TFB作为空穴传输层,量子点作为发光层,采用无机二氧化钛（TiO2）作为电子传输层,在相同的工艺条件下调节量子点层旋涂转速（800～1100 r/min）,制备不同厚度的量子点发光二极管发光器件（QD-LEDs）。实验结果表明,当量子点层的旋涂转速为900 r/min时,此时的量子点层厚度为30 nm,所制备的量子点发光二极管器件（QD-LEDs）的发光性能最好,开启电压最低,只有5．5 V。     

顶发射白光有机电致发光器件的优化

为满足大面积固态照明与全彩显示的需求,实现色度稳定的高效率顶发射白光有机电致发光器件,采用仿真和实验相结合的研究方法,模拟基于光学传输矩阵法和电磁场理论进行计算,用真空蒸镀法制备器件并测试其光电性能。确定传输层材料、厚度和结构,优化发光效率,逐步改进发光层结构,以改善器件的效率和颜色质量。结果表明,基于电学平衡的P-I-N传输结构和蓝/红/蓝三明治型发光结构,能实现色度稳定的高效率顶发射白光有机电致发光器件。     

Red organic light emitting device with improved performance using a novel fluorescent dye codoped with phosphor-sensitizer

Efficient red organic light-emitting device consisted of a compound fluorescent-phosphor-sensitized emission layer was fabricated. A novel red fluorescent dye, 3-(dicyanomethylene)-5,5-dimethyl-1-(4-dimethylamino-styryl) cyclohexene (DCDDC), and a green phosphorescent dye, fac tris(2-phenylpyridine) iridium [Ir(ppy)3] were codoped into a host material 4,4’-N,N’-dicarbazolebiphenyl (CBP). By adjusting the component ratio of doping system, a series of devices with different concentration proportion of Ir(ppy)3:DCDDC were constructed. The results demonstrated that the device with 0.2 wt% DCDDC had a maximum power efficiency (η_p) of 2.12 lm/W at a current density of 0.1 mA/cm², which was about 38% higher than that of conventional fluorescent device. When at a current density of 4 mA/cm2 (100 cd/m²) and 52 mA/cm² (1000 cd/m²), the η_p percentage was about 160% and 143% higher than that of conventional device, respectively. A stable red light emission at a peak of 615 nm with Commissions Internationale de l’Eclairage coordinates near the region of (0.56, 0.42) in a wide bias range was also obtained. The improved performances were attributed to the efficient multiple-stage energy transfer from the host to the guest and the suppression of loss mechanism.     

空穴阻挡层BCP对掺杂型有机发光二极管中磁电导效应的影响

通过在器件复合发光区附近插入空穴阻挡层BCP,制备了一种具有非平衡传输性能的荧光染料掺杂型发光二极管,其结构为ITO／CuPc／NPB／NPB：DCM（5wt％）／BCP／Alq3／LiF／Al,并在不同温度和电压下测量了器件的注入电流随外加磁场的变化（即磁电导效应）．实验结果表现为：当磁场处在0～40mT时,该非平衡发光器件的磁电导随磁场的增加而迅速增大（即表现为快变的正磁电导效应）．这一实验现象与具有相对平衡传输性能的发光器件中所观测到的磁电导效应一致;当磁场大于40mT时,非平衡发光器件的磁电导随磁场的进一步增加表现为缓慢下降（即缓变的负磁电导效应成分）,而平衡器件的磁电导则变为继续缓慢增加（即为缓变的正磁电导效应）．本文对非平衡传输掺杂型发光器件的体系特征进行了讨论,并基于三重态激子-电荷（T-Q）反应受外加磁场的影响对上述实验现象进行了定性解释．     

LiF用作阴极注入层的有机发光二极管制备

使用真空热蒸发方法,制备了结构为ITO/TPD/Alq3/LiF/Al的有机发光二极管,其中LiF用作阴极注入层,LiF超薄层的加入,增强了电子注入,降低了启亮电压,提高了器件的发光效率和亮度. 实验结果表明:当加入LiF层的厚度为0.5 nm时,器件性能的改善最好,和不含LiF的器件相比,启亮电压由原来的9 V降低到5 V,效率由1.5 cd/A增加到3.3 cd/A,提高了近1倍,然而随着加入LiF层厚度的增加,器件性能的改善效果降低.     

有机发光器件中空穴注入对负电容的影响

对不同结构的有机发光器件(OLED)进行了电容-电压(C-V)特性测量,研究了不同空穴注入结构对OLED负电容的影响。结果表明,负电容的产生与OLED内部电场的分布有着密切的关系,负电容开始出现的频率与电压的平方根呈指数关系。与超薄的单层空穴注入层相比,掺杂的空穴注入层不仅能降低器件的驱动电压,而且其载流子传输特性和出现负电容时的初始电压对频率有着更强的依赖性。     

Luminescent and photovoltaic properties of poly（9,9-dioctylfluorene- co-bithiophene） in organic electronic devices

We studied the luminescent and photovoltaic properties of poly(9,9-dioctylfluorene-co-bithiophene)(F8T2) based on ITO/PEDOT:PSS/F8T2/Bphen/LiF(0 or 1 nm)/Al and ITO/PEDOT:PSS/F8T2:PCBM/Bphen/Al.A stable and bright yellow emission was obtained from polymer F8T2,and the electroluminescence power reached 45 ?W at a 15 V driving voltage.Polymer F8T2 shows a broad absorption band from 400 to 500 nm,and has a shorter absorption edge at about 560 nm compared to that of the typical electron donor P3HT(650 nm).The photoluminescence quenching of F8T2 occurs with only a small fraction of blended PCBM due to the effective exciton dissociation at the interface between F8T2 and PCBM.Polymer solar cells(PSCs) using F8T2:PCBM as the active layer show a low power conversion efficiency(PCE) of 0.10% with an open circuit voltage(Voc) of 0.91 V and short circuit current density(Jsc) of 0.23 mA/cm2.The PSCs using F8T2:P3HT:PCBM as the active layer have a Voc of 0.85 V and Jsc of 3.02 mA/cm2,improving the PCE by about 0.90%.We attribute the improved cell performance to the higher number of photons harvested by P3HT molecules.     

白光LED用新型高效红色荧光粉的制备及其发光性能研究

用Na＋做电荷补偿剂,Sm3＋做敏化剂,采用高温固相法制备了Ca0.5MoO4：Eu3＋0.25-x,Sm3＋x,Na＋0.25（x=0,0.001,0.003,0.005,0.008,0.01,0.02,0.03,0.05,0.07,0.09）系列红色荧光粉,实验结果表明：Sm3＋的加入没有改变CaMoO4：Eu3＋,Na＋的晶体结构,也没有改变粉体发射光谱的形状和发射峰的位置,而是加宽了荧光粉CaMoO4：Eu3＋,Na＋激发光谱在400 nm左右的吸收峰,有利于样品的激发峰和近紫外LED芯片相匹配,并且提高了荧光粉在615 nm处发射光谱的发光强度.本文主要对Sm3＋提高荧光粉的发光强度的原理进行探讨,研究结果证明在CaMoO4基质中存在Sm3＋-Eu3＋之间能量传递,此外得出Sm3＋的最佳掺杂浓度是0.5 at.%.     

发射蓝光的氧化多孔硅和氧化硅的比较研究

对发射蓝光的多孔硅和氧化硅样品分别作了光致和光致发光激发光谱的对比研究，结果表明，当氧化温度达到1150℃时，多孔硅中的纳米硅粒完全消失，此时的光致发光激发谱与发射蓝光的氧化硅的光致发光激发谱有相似的结构和峰位。     

利用ITO膜解决AlGaInP LED窗口层电流扩展问题

讨论如何利用隧道效应,应用ITO做电极来减薄发光二极管（LED）窗口层。同时解决了电流扩展问题,并对器件的稳定性作了一定讨论。