有机薄膜器件负电阻特性的影响因素

研究了影响有机染料掺杂聚合物薄膜器件负电阻特性的因素，为探索有机负电阻的机理提供实验依据。实验中制备了多种有机染料掺杂聚合物薄膜器件，研究了有机小分子染料、聚合物基体、薄膜组成及厚度、ITO和聚苯胺阳极等对有机染料掺杂聚合物薄膜器件负电阻特性的影响。在室温、大气环境下，所制备的多种有机染料掺杂聚合物器件在所加电压为3～4V时，观察到明显的负电阻特性，电流峰谷比最大约为8。负电阻现象及峰谷比的大小受膜厚和器件的结构、制备工艺等影响。提出用负电阻和二极管并联组成的等效电路模型解释影响负电阻特性的因素，认为负电阻特性与载流子的不平衡注入有关。在此基础上设计、合成了主链含唔二唑电子传输基团的可溶性聚对苯撑乙烯衍生物，该聚合物兼具空穴和电子传输功能，在空气中具有较稳定的N型负电阻特性。进一步控制相关材料和工艺条件，有可能得到易于控制的负阻效应，开发出新型的有机负电阻器件。     

全湿法制备聚合物白光器件

使用全溶液法制备聚合物白光器件,通过引入修饰层并改变各层薄膜厚度来优化器件性能。针对ITO 阴极功函数较高的问题,引入功函数较低的蓝光聚芴衍生物：聚[9,9-二辛基芴-9,9-双（N,N-二甲基胺丙基）芴]（PFN）,有效地降低了阴极的复合功函数。同时PFN也是电子注入材料和发光材料。为降低器件的启动电压,引入Cs₂CO₃作为修饰层,同时也提高了电子传输能力。使用MEH-PPV作为橙红光材料。使用二次溶剂掺杂获得的高导PEDOT：PSS聚合物并通过滴膜的方法制备阳极取代了传统的金属电极真空镀膜法,从而使器件制备简单、快捷。最终得到了湿法制作的聚合物白光器件的光谱范围为400~800 nm,涵盖了整个可见光区域。器件的启亮电压为4 V,亮度为1 500 cd/m²,电流效率为0.55 cd/A。     

基于咔唑和噻吩的两种聚合物的电化学合成

利用斯蒂尔偶联反应合成了两种基于咔唑和噻吩的有机共轭单体,通过电化学方法聚合成导电聚合物,并对其进行了结构表征和光电性能研究. 核磁共振¹H谱和¹³C谱验证了单体与理论结构一致,红外测试验证了电化学聚合位点为噻吩的α位. 光滑、均质且分布小孔的表面形貌有利于提高聚合物的电导率和电子传输性能. 在-0.1 V到1.2 V电压范围内,两种聚合物膜都表现出良好的电致变色特性. 循环伏安法和热重表明,相比于聚合物P1,共平面性更好的聚合物P2的电化学和热稳定性更优.     

空间电荷限制电流法测量共混体系中空穴的迁移率

载流子迁移率测量是有机半导体材料与器件研究中的重要内容之一.以聚噻吩为电子给体材料, C₆₀的衍生物为电子受体材料,制备了一种单电荷传输器件.用空间电荷限制电流法测出了不同溶剂形成的 活性层及不同温度热处理后器件中空穴的迁移率.结果表明:器件中电荷的传输J-V曲线符合Mott-Gurney方程, 不同溶剂形成活性层中空穴具有不同的迁移率,高沸点的溶剂1, 2-二氯苯形成的活性层具有较高的空穴迁移率, 热处理有利于器件中空穴迁移率的提高.同时还进一步分析了空穴迁移率变化的原因.     

共轭聚合物作为有机光电池电子受体的特性研究

以聚3-已基噻吩(P3HT)和聚对苯亚乙烯衍生物(MDMO-PPV)作为电子给体,聚 (TQ1)作为电子受体,制备并研究了聚合物给体/聚合物受体有机光伏电池性能。当给体P3HT、受体TQ1共混质量比为1∶1时,器件性能最佳。热处理会改变薄膜形貌,导致激子扩散到达界面的距离增加和激子分离界面数量下降,进而引起器件性能下降。溶剂效应对器件性能影响不明显。研究了相似能带结构给体聚合物对MDMD-PPV光电池性能的影响,发现结晶程度较低的给体材料会进一步导致器件性能降低。     

铽配合物Tb(BA)3phen的有机电致发光

合成了一类新型稀土配合物Tb(BA)3phen,将其掺杂到导电聚合物PVK中获得了纯正、明亮的绿光发射.用这种搀杂体系分别制作了单层发光器件和双层器件.对于单层器件,掺杂浓度为15,甩膜转速1000 r·min-1时器件的发光效果最好,起亮电压为10V,最大亮度在21 V时可达26.8cd·m-2.双层器件用AlQ作为电子传输层,通过改变其厚度得到了发光性能较好的用AlQ作为电子传输材料的器件,其最大亮度在22 V时可达322cd·m-2.     

基于Spiro-OMeTAD电子阻挡层的量子点发光二极管电荷平衡改善

针对量子点发光二极管空穴传输层和电子传输层的迁移率差异而导致的电荷不平衡问题,将具有最低未占分子轨道高能级的有机聚合物Spiro-OMeTAD薄膜放置在空穴传输层与量子点发光层之间,阻挡过剩电子由量子点发光层向空穴传输层的传输,促进器件的电荷平衡,制备出一种高效的新型绿色量子点发光二极管。结果表明:相比于传统器件,新型绿色量子点发光二极管器件的外部量子效率提升了87%,达到11.87%,亮度提升了106%,达到53055cd/m~2;阻挡过剩电子的传输可以显著改善器件中的电荷不平衡现象。     

室温生长AZO/Al_2O_3叠层薄膜晶体管性能研究

针对目前大多数氧化物薄膜晶体管都需要采用热退火工艺来提高其性能不利于其在柔性显示器件中应用这一问题,提出了一种采用室温工艺制备的新型TFT器件,无需退火处理即可获得较好的器件性能。该器件采用脉冲激光沉积技术制备的AZO/Al_2O_3叠层结构作为沟道层。与单层AZO-TFT器件相比,叠层TFT器件具有更优异的性能,其迁移率为2.27 cm2·V-1·s-1,开关比为1.43×106。通过对AZO/Al_2O_3叠层薄膜的厚度、密度、粗糙度、物相、界面特性及能带结构等进行分析,发现这种叠层结构能够使电子的运动被限制在AZO薄膜平面内,即形成了二维电子传输,从而提升TFT器件的性能。     

CBP有机薄膜对MEH-PPV聚合物发光二极管性能的影响

以聚合物发光材料MEH-PPV为发光层的聚合物发光二极管的ITO阳极与发光层之间,加入一层溶解于氯仿中的有机小分子CBP,能显著改善发光器件的电流特性。在电压较低的时候能提高电流,在电压较高的时候能抑制电流,从而增加工作电压范围。此外,器件的电流效率也能得到显著的提高。实验结果表明,加入CBP层后,在低电压时,CBP层能够减缓空穴注入到发光层中,将其限制在CBP层,从而在器件中形成一个内电场,有助于电子的传输,降低开启电压,提高发光亮度。在电压较高时,CBP作为电子阻挡层,能阻挡电子漏泄到阳极,从而使在复合区的空穴与少数载流子电子的复合效率提高,改善器件的性能。     

NiO_x作为空穴传输层对有机太阳能电池光吸收的影响

基于多层膜系模型的传输矩阵方法、麦克斯韦方程和光子吸收方程,研究了NiOx作为替代3,4-乙撑二氧噻吩:聚苯乙烯磺酸盐(PEDOT:PSS)的空穴传输材料对聚3-己噻吩(P3HT)和富勒烯衍生物([6,6]-phenyl-C61-butyric acid methyl ester,PC61BM)共混体异质结有机太阳能电池器件内部光电场分布和光吸收特性的影响.分别制备了以NiOx和PEDOT:PSS为空穴传输层,P3HT:PCBM为活性层的有机太阳能电池,并通过数值模拟的方法比较了NiOx和PEDOT:PSS两种空穴传输材料对器件光伏特性的影响.结果表明:10 nm的NiOx空穴传输层器件比40 nm的PEDOT:PSS器件获得了更大的短路电流和填充因子,并具有更高的能量转化效率.     

制膜工艺对聚合物太阳电池性能影响的研究

用渡越时间法（TOF）分别测试了采用旋涂和滴涂方法制备的poly［2-methoxy-5-（2′-ethylhexyloxy）-1,4- phenylenevinylene］（MEH-PPV）薄膜的空穴迁移率,用原子力显微镜对这两种方法制备的薄膜表面形貌进行了研究.结果表明使用滴涂法有利于聚合物形成有序薄膜结构,能有效提高空穴迁移率.用滴涂法制备的基于MEH-PPV：phenyl C61- butyric acid methyl ester（PCBM）共混薄膜的太阳电池,对比用旋涂法制备的太阳电池,其能量 关键词： 太阳电池 聚合物 迁移率     

DFT/TDDFT investigation on the photophysical properties of a series of phosphorescent cyclometalated complexes based on the benchmark complex FIrpic

The photophysical properties of four Ir(III) complexes have been investigated by means of the density functional theory/time-dependent density functional theory (DFT/TDDFT). The effect of the electron-withdrawing and electron-donating substituents on charge injection, transport, absorption and phosphorescent properties has been studied. The theoretical calculation shows that the lowest-lying singlet absorptions for complexes 1–4 are located at 387, 385, 418 and 386 nm, respectively. For 1–4, the phosphorescence at 465, 485, 494 and 478 nm is mainly attributed to the LUMO → HOMO and LUMO → HOMO-1 transition configurations characteristics. In addition, ionisation potential (IP), electron affinities (EAs) and reorganisation energy have been investigated to evaluate the charge transfer and balance properties between hole and electron. The balance of the reorganisation energies for complex 3 is better than others. The difference between hole transport and electron transport for complex 3 is the smallest among these complexes, which is beneficial to achieve the hole and electron transfer balance in emitting layer.     

混合发光层有机电致发光器件中的多重成分发射

以等摩尔空穴传输材料TPD和电子传输材料PBD组成结构为ITO/TPD/TPD∶PBD/PBD/Al的混合物发光层有机电致发光(EL)器件,观察到了相对于组成材料的荧光光谱红移的宽发射带。通过比较EL光谱,光致发光光谱及EL光谱分解,表明电致发光中同时包含单体发射、激基复合物和电荷对复合物的发射。激基复合物为TPD的激发态TPD*与PBD的基态相互作用形成TPD*PBD类型的复合物,电荷对复合物是带电荷的空穴传输分子(D+)的空穴和电子传输分子(A-)的电子交叉复合而形成的(D+-A-)*复合物。各激发态在电场作用下呈现不同的形成机理和复合过程,并且单体发射和激发态复合物的比例随电场而变化,导致发射光谱随电场增强而蓝移。该器件的最高亮度和最大外部量子效率分别为240 cd·(cm2)-1和0.49%。有机固态界面激基复合物或电荷对复合物的发射常出现宽的红移发射带,是调节发光颜色的有效手段。     

Improved performance of polymer solar cells by using inorganic,organic, and doped cathode buffer layers

The interface between the active layer and the electrode is one of the most critical factors that could affect the device performance of polymer solar cells. In this work, based on the typical poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methyl ester(P3HT:PCBM) polymer solar cell, we studied the effect of the cathode buffer layer(CBL) between the top metal electrode and the active layer on the device performance. Several inorganic and organic materials commonly used as the electron injection layer in an organic light-emitting diode(OLED) were employed as the CBL in the P3HT:PCBM polymer solar cells. Our results demonstrate that the inorganic and organic materials like Cs_2CO_3, bathophenanthroline(Bphen), and 8-hydroxyquinolatolithium(Liq) can be used as CBL to efficiently improve the device performance of the P3HT:PCBM polymer solar cells. The P3HT:PCBM devices employed various CBLs possess power conversion efficiencies(PCEs) of 3.0%–3.3%, which are ca. 50% improved compared to that of the device without CBL. Furthermore, by using the doped organic materials Bphen:Cs_2CO_3 and Bphen:Liq as the CBL, the PCE of the P3HT:PCBM device will be further improved to 3.5%, which is ca. 70% higher than that of the device without a CBL and ca. 10% increased compared with that of the devices with a neat inorganic or organic CBL.     

Bipolar Alq3-based complexes: Effect of hole-transporting substituent on the properties of Alq3-center

Two bipolar Alq₃-based complexes, tris{5-[(carbazole-9'-yl)methyl]-8-hydroxyquinoline} aluminum (Al(CzHQ)₃) and tris{5-[(phenothiazine-9'-yl)methyl]-8-hydroxyquinoline} aluminum (Al(PHQ)₃), involving an Alq₃-center and three hole-transporting substituents (carbazole or phenothiazine), were prepared and characterized. Effects of hole-transporting substituent on the properties of Alq₃-center were investigated in detail. It is found that the two complexes have improved hole-transporting performance and appropriate thermal stability (the 5%-weight-loss temperatures T_5%>260 ^oC). Photoluminescence (PL) spectra indicate that both energy transfer and electron transfer can take place simultaneously in the PL process of these complexes. Both thermodynamics and dynamics of the electron transfer were studied and corresponding parameters were calculated. Energy transfer is favorable for the PL of Alq₃-center, while electron transfer is unfavorable for the PL of Alq₃-center. These results will be useful to explore novel OLEDs material with increased efficiency.     

Efficiency of a blue organic light-emitting diode enhanced by inserting charge control layers into the emission region

We demonstrate high current efficiency of a blue fluorescent organic light-emitting diode (OLED) by using the charge control layers (CCLs) based on Alq3 . The CCLs that are inserted into the emitting layers (EMLs) could impede the hole injection and facilitate the electron transport, which can improve the carrier balance and further expand the exciton generation region. The maximal current efficiency of the optimal device is 5.89 cd/A at 1.81 mA/cm2 , which is about 2.19 times higher than that of the control device (CD) without the CCL, and the maximal luminance is 19.660 cd/m2 at 12V. The device shows a good color stability though the green light emitting material Alq3 is introduced as the CCL in the EML, but it has a poor lifetime due to the formation of cationic Alq3 species.     

含噻二唑聚芴类白光聚合物的合成与发光性能研究

通过Suzuki偶联反应将2,7-二溴-9,9-二辛基芴（Br-DOF）、2,7-二硼酸-9,9-二辛基芴（B-DOF）和4-（8-（2,7-二溴-9-辛基芴）辛氧基）-N-4-（7-（4-（二苯胺基）苯基）苯并噻二唑）苯基-二苯胺（Br-TAF）共聚,合成了白光聚合物PDOF-TAF。以PDOF-TAF为发光层,溶液旋涂制备了非掺杂型单层白光有机电致发光二极管,色坐标为（0.23,0.18）。通过插入电子传输层TPBI和空穴传输层PVK得到的白光器件发射光谱覆盖了410~700 nm区域,色坐标从（0.23,0.18）调整到（0.24,0.32）,亮度达到2 020 cd/m²,电流效率达到1.4 cd/A。实验结果表明,PDOF-TAF是一种很好的白光聚合物发光材料,在WOLED中将有很好的应用前景。     

Determination of sulfoxide bond dissociation enthalpies of dibenzothiophene S‐oxide derivatives with computational methods

Photodeoxygenation of dibenzothiophene S‐oxide (DBTO) has been suggested as a clean way to generate atomic oxygen in solution. Sulfoxide bond dissociation enthalpies (BDEs) are important to the quantum yield and mechanism of this photodeoxygenation. In this study, BDE of substituted DBTO molecules with various functional groups were determined using M062X/aug‐cc‐pV(T + d)Z and MP2/aug‐cc‐pV(T + d)Z levels of theory. The sulfoxide BDE was determined using an isodesmic reaction. The observed effect of substitution was that functional groups with negative σ_para values (electron donating) strengthen the sulfoxide bond and that substituents with positive σ_para values (electron withdrawing) weaken the sulfoxide bond. The Mulliken charge on sulfur for DBTO and the corresponding dibenzothiophene were identified as a suitable indicator of the predicted S–O BDE. Moreover, steric and hydrogen bonding interactions were found to affect sulfoxide BDE for certain functional groups when located at the 1 or 4 positions of the substituted DBTO. Copyright © 2014 John Wiley & Sons, Ltd.     

Significant improvement of OLED efficiency and stability by doping both HTL and ETL with different dopant in heterojunction of polymer/small-molecules

This paper reports that the polymer/organic heterojunction doped light-emitting diodes using a novel poly-TPD as hole transport material and doping both hole transport layer and emitter layer with the highly fluorescent rubrene and DCJTB has been successfully fabricated. The basic structure of the heterostructure is PTPD/Alq₃. When hole transport layer and electron transport layer are doped simultaneously with different dopant, the electroluminescence quantum efficiencies are about 3 times greater than that of the undoped device. Compared with undoped device and conventional TPD/Alq₃ diode, the stability of the doping device is significantly improved. The process of emission for doped device may include carrier trapping as well as F\"{o}rster energy transfer.     

Theoretical study of the optical and charge transport properties in non-peripherally octasubstituted phthalocyanine–tetrabenzoporphyrin hybrids

The charge transfer rate of seven non-peripherally phthalocyanine–tetrabenzoporphyrin hybrids was investigated theoretically at the level of B3LYP/6-31+G(d,p) using density functional theory. The results showed that the hybrids are semiconductor molecules, which have a certain absorption in the visible region. The hole or electron transport capability of a non-peripherally substituted octamethyl phthalocyanine molecule is obviously better than that of phthalocyanine or non-peripherally substituted octafluorine, octamethoxy phthalocyanine molecules at 300 K, whereas the holes or electron transport capabilities of four non-peripherally substituted octamethoxy phthalocyanine–tetrabenzoporphyrin hybrids are basically the same. Overall, the hole transport capability of hybrids is superior to their electron transport capability. The charge transfer rate constant and the carrier mobility rate of three representative molecules using three methods, that is the long range-corrected functionals CHB-B3LYP and WB97XD, the metahybrid GGA M06-2X functional, are consistent with the use of the density functional B3LYP method.