利用PtOEP掺杂改善Spiro发光器件的发光效率

为了利用有机三线态发光提高有机发光器件的发光效率,用磷光材料掺杂到聚合物主体中作为发光层,制备有机电致发光器件.在测量器件的电流-电压特性、发光亮度-电压特性和电致发光谱的基础上,计算了器件的外量子效率,研究了磷光材料的掺杂浓度对器件发光效率的影响.结果表明,对特定的材料体系,适当控制掺杂浓度,可以同时观察到荧光和磷光光谱,使掺杂器件的外量子效率在纯聚合物发光器件的基础上得到明显提高.     

蓝光聚合物共混材料的发光特性

研究了不同组成 PVK和 P6 共混材料薄膜的光吸收特性和光致发光特性 .用不同比例 PVK∶ P6 共混材料为发光层和 Alq3为电子传输层合成双层结构的蓝光器件 ,测量器件的电致发光谱、电流 -电压特性和亮度 -电压特性 .结果表明 ,共混材料的光致发光强度比 PVK和 P6 都有明显的增强 ,且随 PVK浓度的增加而增强 ;器件电致发光强度随 PVK浓度的增加而增强 ;不同 PVK掺杂浓度对电致发光器件的开启特性没有明显影响 ,发光亮度随 PVK掺杂浓度的增加而增大 .     

蓝光聚合物共混材料的发光特性

研究了不同组成PVK和P6共混材料薄膜的光吸收特性和光致发光特性．用不同比例PVK∶P6共混材料为发光层和Alq3为电子传输层合成双层结构的蓝光器件,测量器件的电致发光谱、电流-电压特性和亮度-电压特性．结果表明,共混材料的光致发光强度比PVK和P6都有明显的增强,且随PVK浓度的增加而增强;器件电致发光强度随PVK浓度的增加而增强;不同PVK掺杂浓度对电致发光器件的开启特性没有明显影响,发光亮度随PVK掺杂浓度的增加而增大．     

蓝绿色磷光OLED的制备及发光性能研究

以mCP为主体发光材料,蓝绿色磷光染料BGIr1作为掺杂剂,制备了6种不同BGIr1掺杂量的蓝绿色磷光有机电致发光器件(OLED),研究了不同掺杂量对蓝绿色磷光OLED器件发光特性的影响。制得器件的结构为ITO/MoO3(20nm)/NPB(40nm)/mCP:BGIr1(x%,30nm)/BCP(10nm)/Alq3(20nm)/LiF/Al(100nm),其中x%为发光层中磷光染料BGIr1的掺杂量(质量分数)。结果表明,BGIr1掺杂量为18%时,获得器件的发光性能最佳。18%BGIr1掺杂器件在488nm和512nm处获得两个主发射峰,当电流密度为26.5mA/cm2时,获得最大发光效率为6.2cd/A;在15V驱动电压下,获得最大亮度为6 970cd/cm2,CIE坐标为(0.17,0.31)。这说明,BGIr1掺杂改善了器件的发光亮度和色纯度,提高了器件的发光效率。     

掺杂与非掺杂相结合制备有机发光器件

采用掺杂和非掺杂方法制备了一种多层白色有机电致发光器件.DPVBi为蓝光发光层,将红光[Ir(piq)2(acac)]磷光掺杂染料掺入到母体BAlq中作为红光发光层,荧光材料QAD以亚单层的方式插入Alq3中作为绿光发光层,通过改变亚单层的厚度,得到了高效率的有机发光器件,此器件的最大电流效率可达6.1 cd/A,最大功率效率达3.1 lm/W,最大亮度达25 300 cd/m2,当电压从4V变化到14V时,色坐标从(0.45,0.55)变化到(0.47,0.37),处于黄白光区.此器件的特点在于器件的性能可以通过简单地调整QAD的厚度进行控制,避免了使用多掺杂层工艺的复杂性.     

蓝绿色磷光OLED的制备及发光性能研究

以mCP为主体发光材料,蓝绿色磷光染料BGIr1作 为掺杂剂,制备了6种不同BGIr1掺杂量的蓝绿色磷光有机电致发光器件(OLED),研究了不 同掺杂量对蓝绿色磷光OLED器件发光特性的影 响。制得器件的结构为ITO/MoO₃(20nm)/NPB(40nm)/mCP:BGIr1(x%,30nm)/BCP(10nm)/Alq₃(20 nm)/LiF/Al(100nm),其中x%为发光层中磷光染料BGIr1的掺杂量(质量分数)。结果表明,BGIr1掺杂量 为18%时,获得器件的发光性能最佳。18% BGIr 1掺杂器件在488nm和 512nm处获得两个主发射峰,当电 流密度为26.5mA/cm²时,获得最大发光效率为6.2cd/A;在15V驱动电压下,获得最大亮度为6970cd/cm², CIE坐标为(0.17,0.31)。这说明,BGI r1掺杂改善了器件的发光亮度和色纯度,提高了器件的发光效率。     

驱动方式对磷光器件的影响

制备了以聚合物为主体的磷光掺杂型有机电致发光器件，通过引入空穴阻挡层改善了载流子注入平衡，从而改善了器件的发光性能，通过比较直流和不同频率交流驱动下的电致发光．发现器件的发光随交流驱动电压的频率增大而减小。分析认为，频率影响到对空穴和电子的渡越时间。进而影响到其复合发光的几率。     

一种基于液晶性质的Pt配合物磷光材料电致发光器件

采用聚合物掺杂的方式,利用旋涂工艺制备了ITO/PVK:TOPPt/BCP(20 nm)/Mg:Ag(200 nm)结构的有机电致发光器件(OLED)。对掺杂浓度为2%(器件A)和4%(器件B)的磷光聚合物掺杂体系的光致发光(PL)和电致发光(EL)性质进行了分析研究,并对主体材料PVK到磷光客体材料TOPPPt的能量传递机制进行了讨论。实验表明,器件的EL谱谱峰位于625 nm,器件A在25 V时最大亮度为3037 cd/m2,最大电流效率为3.15cd/A。器件的EL谱不会随着偏置电压和掺杂浓度而改变,器件具有较好的稳定性。     

发光层掺杂蓝色OLED的光电性能研究

采用真空热蒸镀技术,在不同的掺杂浓度下,制备了4种双异质型结构的蓝色有机电致发光器件(OLED),其结构为ITO/CuPc(30 nm)/NPB(40 nm)/TPBi(30 nm):GDI691(x%)/Alq3(20 nm)/LiF(1 nm)/Al(50 nm),其中x%为发光层掺杂浓度,分别取1、2、3和4 %.从实验结果分析可知:蓝色OLED的电流-电压(I-V)特性曲线、亮度-电压(L-V)曲线、亮度-电流(L-I)曲线及效率等光电性能随着发光层掺杂浓度的变化而改变.当驱动电压为15 V、掺杂浓度为3%时,器件可获得最大亮度6100 cd·m-2,色坐标CIE为x=0.147、y=0.215,最大流明效率为1.221 m·W-1,电致发光(EL)发光光谱的峰值为468 nm.     

聚合物/有机小分子异质结掺杂型电致发光二极管及其发射机制

为了提高有机电致发光器件的效率和稳定性,制作了聚合物/有机小分子异质结掺杂型电致发光二极管.它以新型PTPD(聚TPD)为空穴传输材料,高效荧光材料Rubrene为掺杂剂.异质结基本结构为PTPD/Alq3,双层掺杂时,器件电致发光的量子效率大约是未掺杂器件的两倍;与未掺杂器件和常用的TPD/Alq3二极管相比,掺杂器件的稳定性有了显著的提高.从电致发光光谱可知,掺杂器件的发射机制为载流子陷阱和Forster能量转换过程的共同作用.     

Highly efficient electrophosphorescent polymer light-emitting devices

We report a high performance polymer electroluminescent device based on a bi-layer structure consisting of a hole transporting layer (poly(vinylcarbazole)) and an electron transporting layer poly(9,9-bis(octyl)-fluorene-2,7-diyl) (BOc-PF) doped with platinum(II)-2,8,12,17-tetraethyl-3,7,13,18-tetramethylporphyrin (PtOX). The devices show red electrophosphorescence with a peak emission at 656 nm and a full width at half maximum of 18 nm, consistent with exclusive emission from the PtOX dopants. BOc-PF emission is not observed at any bias. The required doping levels for these phosphorescence-based polymer light-emitting diodes (PLEDs) are significantly lower than for other reported phosphorescence-based PLEDs or organic light-emitting diodes (OLEDs). A doping level of 1% or more give an LED with exclusive PtOX emission, whereas related PLEDs or OLEDs doped with phosphorescent dopants require doping levels of >5% to achieve exclusive dye dopant emission. The device external efficiency was enhanced from 1% to 2.3% when doped with PtOX. The lower doping level in BOc-PF/PtOX based PLEDs decreases triplet–triplet annihilation in these devices, leading to quantum efficiency that is only weakly dependent on current density. The luminescence transient decay time for this device is 500 μs.     

Indenocarbazole based bipolar host materials for highly efficient yellow phosphorescent organic light emitting diodes

We report bipolar host materials with robust indenocarbazole and biphenyl moiety as hole-electron-transporting unit for phosphorescent yellow organic light-emitting diodes (OLEDs). New host materials demonstrated an excellent morphological stability with high glass transition temperature of 207 °C. Simultaneously, it also revealed appropriate triplet energy of about 2.6 eV for ideal triplet energy transfer to yellow phosphorescent dopant. A phosphorescent yellow OLED with new host ICBP1 (and ICBP2) and conventional yellow dopant iridium(III)bis(4-(4-t-butylphenyl)thieno[3,2-c]pyridinato-N,C2′)acetylacetonate (Ir(tptpy)₂acac) shows a low driving voltage of 3.4 (and 3.6 V) at 1000 cd/m², and maximum external quantum efficiency as high as 26.4%. Such efficient performance of phosphorescent yellow OLEDs is attributed to a good charge balance and high electron transport properties of host materials.     

Low Roll‐Off and High Efficiency Orange Organic Light Emitting Diodes with Controlled Co‐Doping of Green and Red Phosphorescent Dopants in an Exciplex Forming Co‐Host

An exciplex forming co‐host is introduced in order to fabricate orange organic light‐emitting diodes (OLEDs) with high efficiency, low driving voltage and an extremely low efficiency roll‐off, by the co‐doping of green and red emitting phosphorescence dyes in the host. The orange OLEDs achieves a low turn‐on voltage of 2.4 V, which is equivalent to the triplet energy gap of the phosphorescent‐green emitting dopant, and a very high external quantum efficiency (EQE) of 25.0%. Moreover, the OLEDs show low efficiency roll‐off with an EQE of over 21% at 10 000 cdm^?2. The device displays a very good orange color (CIE of (0.501, 0.478) at 1000 cdm^?2) with very little color shift with increasing luminance. The transient electroluminescence of the OLEDs indicate that both energy transfer and direct charge trapping takes place in the devices.     

Exciplex‐Forming Co‐host for Organic Light‐Emitting Diodes with Ultimate Efficiency

Phosphorescent organic light‐emitting diodes (OLEDs) with ultimate efficiency in terms of the external quantum efficiency (EQE), driving voltage, and efficiency roll‐off are reported, making use of an exciplex‐forming co‐host. This exciplex‐forming co‐host system enables efficient singlet and triplet energy transfers from the host exciplex to the phosphorescent dopant because the singlet and triplet energies of the exciplex are almost identical. In addition, the system has low probability of direct trapping of charges at the dopant molecules and no charge‐injection barrier from the charge‐transport layers to the emitting layer. By combining all these factors, the OLEDs achieve a low turn‐on voltage of 2.4 V, a very high EQE of 29.1% and a very high power efficiency of 124 lm W^?1. In addition, the OLEDs achieve an extremely low efficiency roll‐off. The EQE of the optimized OLED is maintained at more than 27.8%, up to 10 000 cd m^?2.     

Ideal host and guest system in phosphorescent OLEDs

Ideal host-guest system for emission in phosphorescent OLEDs with only 1% guest doping condition for efficient energy transfer have been demonstrated in the present investigation. Using a narrow band-gap fluorescent host material, bis(10-hydroxybenzo[h] quinolinato)beryllium complex (Bebq₂), and red dopant bis(2-phenylquinoline)(acetylacetonate)iridium (Ir(phq)₂acac), highly efficient red phosphorescent OLEDs (PHOLEDs) exhibiting excellent energy transfer characteristics with a doping concentration of 1% were developed. Fabricated PHOLEDs show a driving voltage of 3.7 V, maximum current and power efficiencies of 26.53 cd/A and 29.58 lm/W, and a maximum external quantum efficiency of 21%. Minimized electron or hole trapping at the phosphorescent guest molecules and efficient Förster and Dexter energy transfers from the Bebq₂ host singlet and triplet states to the emitting triplet of Ir(phq)₂acac guest appear to be the key mechanism for ideal phosphorescence emission.     

Efficient single layer RGB phosphorescent organic light-emitting diodes

We report efficient single layer red, green, and blue (RGB) phosphorescent organic light-emitting diodes (OLEDs) using a “direct hole injection into and transport on triplet dopant” strategy. In particular, red dopant tris(1-phenylisoquinoline)iridium [Ir(piq)₃], green dopant tris(2-phenylpyridine)iridium [Ir(ppy)₃], and blue dopant bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl)iridium [FIrpic] were doped into an electron transporting 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi) host, respectively, to fabricate RGB single layer devices with indium tin oxide (ITO) anode and LiF/Al cathode. It is found that the maximum current efficiencies of the devices are 3.7, 34.5, and 6.8 cd/A, respectively. Moreover, by inserting a pure dopant buffer layer between the ITO anode and the emission layer, the efficiencies are improved to 4.9, 43.3, and 9.8 cd/A, respectively. It is worth noting that the current efficiency of the green simplified device was as high as 34.6 cd/A, even when the luminance was increased to 1000 cd/m² at an extremely low applied voltage of only 4.3 V. A simple accelerated aging test on the green device also shows the lifetime decay of the simplified device is better than that of a traditional multilayered one.     

Modification of Exciton Lifetime by the Metal Cathode in Phosphorescent OLEDs,and Implications on Device Efficiency and Efficiency Roll‐off Behavior

Time resolved photoluminescence and electroluminescence measurements are used to study changes in the emission characteristics of materials typically used in phosphorescent organic light emitting devices (PhOLEDs). Studies on archetypical PhOLEDs with phosphorescent material, fac‐tris(2‐phenylpyridine) iridium (Ir(ppy)₃), show that the lifetime of triplet exciton is modified when in close proximity to a metal layer. Interactions with a metal layer ～30–100 nm away, as is typically the case in PhOLEDs, result in an increase in the spontaneous emission decay rate of triplet excitons, and causes the exciton lifetime to become shorter as the distance between the phosphorescent material and the metal becomes smaller. The phenomenon, possibly the result of the confined radiation field by the metal, affects device efficiency and efficiency roll‐off behavior. The results shed the light on phenomena affecting the efficiency behavior of PhOLEDs, and provide new insights for device design that can help enhance efficiency performance.     

Phosphorescent dye-doped hole transporting layer for organic light-emitting diodes

Hole transport materials are critical to the performance of organic light-emitting diodes (OLEDs). While 1,1-bis(di-4-tolylaminophenyl)cyclohexane (TAPC) with a high triplet energy is widely used for high efficiency phosphorescent OLEDs, devices using TAPC as a hole transport layer (HTL) have a short operating lifetime due to the build-up of trapped charges at the TAPC/emitting layer (EML) interface during device operation. In this work, to solve the operating stability problem, instead of using conventional HTLs, we use a(fac-tris(2-phenylpyridine)iridium (III))(Ir(ppy)₃) doped layer as an HTL to replace the conventional HTLs. Because of the hole injecting and transporting abilities of the phosphorescent dye, holes can be directly injected into the emitting layer without an injection barrier. OLEDs based on a phosphorescent dye-doped HTL show significant improvement in operational stability without loss of efficiency.     

Ultrahigh Efficiency Fluorescent Single and Bi‐Layer Organic Light Emitting Diodes: The Key Role of Triplet Fusion

A new family of anthracene core, highly fluorescent emitters is synthesized which include diphenylamine hole transport end groups. Using a very simple one or two layer organic light emitting diode (OLED) structure, devices without outcoupling achieve an external quantum efficiency of 6% and photonic efficiencies of 20 cd/A. The theoretical maximum efficiency of such devices should not exceed 3.55%. Detailed photophysical characterization shows that for these anthracene based emitters 2T₁≤T_n and so in this special case, triplet fusion can achieve a singlet production yield of 0.5. Indeed, delayed electroluminescence measurements show that triplet fusion contributes 59% of all singlets produced in these devices. This demonstrates that when triplet fusion becomes very efficient, fluorescent OLEDs even with very simple structures can approach an internal singlet production yield close to the theoretical absolute maximum of 62.5% and rival phosphorescent‐based OLEDs with the added advantage of much improved stability.