Transient demonstration of exciton behaviours in solid state cathodoluminescence under different driving voltage

In the solid state cathodoluminescence (SSCL), organic materials were excited by hot electrons accelerated in silicon oxide (SiO₂) layer under alternating current (AC). In this paper exciton behaviours were analysed by using transient spectra under different driving voltages. The threshold voltages of SSCL and exciton ionization were obtained from the transient spectra. The recombination radiation occurred when the driving voltage went beyond the threshold voltage of exciton ionization. From the transient spectrum of two kinds of luminescence (exciton emission and recombination radiation), it was demonstrated that recombination radiation should benefit from the exciton ionization.     

Effects of concentration and annealing on the performance of regioregular poly（3-hexylthiophene） field-effect transistors

This paper investigates the effects of concentration on the crystalline structure, the morphology, and the charge carrier mobility of regioregular poly(3-hexylthiophene) (RR-P3HT) field-effect transistors (FETs). The RR-P3HT FETs with RR-P3HT as an active layer with different concentrations of RR-P3HT solution from 0.5~wt% to 2~wt% are prepared. The results indicate that the performance of RR-P3HT FETs improves drastically with the increase of RR-P3HT weight percentages in chloroform solution due to the formation of more microcrystalline lamellae and bigger nanoscale islands. It finds that the field-effect mobility of RR-P3HT FET with 2~wt% can reach 5.78× 10^-3~cm²/Vs which is higher by a factor of 13 than that with 0.5~wt%. Further, an appropriate thermal annealing is adopted to improve the performance of RR-P3HT FETs. The field-effect mobility of RR-P3HT FETs increases drastically to 0.09~cm²/Vs by thermal annealing at 150~℃, and the value of on/off current ratio can reach 10^4.     

Ir(ppy)3掺杂PVK体系发光特性的研究

对常温下磷光染料Ir(ppy)3掺杂PVK薄膜的光致发光(PL)和电致发光(EL)特性进行了研究。器件结构为ITO/PEDOT:PSS/PVK:Ir(ppy)3/BCP/Alq3/Al。实验发现随磷光材料掺杂浓度的不同,器件的发光性能发生变化。当浓度适宜时,主体材料PVK的发光很弱,主要为Ir(ppy)3的磷光发射。通过L-I-V特性曲线的比较,掺杂浓度为5%的光电性能最好,说明器件在掺杂浓度为5%时效果最佳。     

Si3N4做电子加速层的聚[2-甲氧基-5-(2-乙基-己氧基)-1,4-苯撑乙烯撑]固态阴极射线发光

用Si3N4作为电子加速层制备了固态阴极射线发光器件,其中发光层为聚[2-甲氧基-5-(2-乙基-己氧基)-1,4-苯撑乙烯撑](MEH-PPV).在交流电压的驱动下,实现了MEH-PPV的固态阴极射线发光.与SiO2做电子加速层的器件进行了对比研究,两种器件在交流电场的驱动下都得到了波峰位于417 nm的短波长发光峰,它来自有机物中电子从最低未占分子轨道到最高占据分子轨道的直接复合发光,这进一步证明了固态阴极射线理论的正确性.在交流高场下比较了Si3N4和SiO2的电子加速能力,发现SiO2的电子加速能力要优于Si3N4的电子加速能力.     

一种新型有机聚合物深红色发光材料的合成及发光特性的研究

合成了一种深红色发光的聚苯乙烯喹啉(PPV-Q)材料,研究了其光致发光,电致发光及吸收光谱。这种材料在紫外和蓝光区具有很强的吸收能力,波长为463 nm的光对此材料具有最高的激发能力。用此材料作为发光层制备了ITO/PPV-Q/Al结构的电致发光器件,发光光谱的中心波长为670 nm,发光光谱的半高全宽为90 nm左右。在不同驱动电压下,器件电致发光的色坐标(x=0.67, y=0.32)基本上没有变化, 是一种深红色的电致发光。器件中的电流随驱动电压的增加而明显增强,导致器件稳定性的降低。     

Electroluminescence quenching mechanism in Rubrene doped host-guest system

In this paper, the electroluminescence quenching mechanism in a 5,6,11,12-tetraphenylnaphthacene (Rubrene) doped host--guest system is studied by utilizing a specially designed organic light-emitting diode with an emission layer consisting of a few periodic host/guest structures. Tris-(8-hydroxyquinoline) aluminium (Alq₃) and Rubrene are used as the host and the guest, respectively. The thickness variation of the guest layer in each period enables the study of the effect of molecule aggregation, and the thickness variation of the host layer suggests a long range quenching mechanism of dipole--dipole interaction. The long range quenching mechanism is a F?rster process, and the F?rster radius of Rubrene is between 3 and 10~nm.     

Enhanced performance in organic photovoltaic devices with KMnO4 solution treated indium tin oxide anode modification

The properties of poly(3-hexylthiophene):(6,6)-phenyl C₆₁ butyric acid methyl ester (P3HT:PCBM) organic photovoltaic devices (OPVs) with indium tin oxide (ITO) anode treated by KMnO₄ solution are investigated. The optimized KMnO₄ solution has a concentration of 50 mg/L, and ITO is treated for 15 min. The modification of ITO anode results in an enhancement of the power conversion efficiency (PCE) of the device, which is responsible for the increase of the photocurrent. The performance enhancement is attributed to the work function modification of the ITO substrate through the strong oxygenation of KMnO₄, and then the charge collection efficiency is improved.     

有机磷光材料的固态阴极射线发光研究

采用有机磷光材料三-(2-苯基吡啶)-铱(Ir(PPY)₃)与无机材料SiO₂复合制成夹层结构器件,用交流电压驱动获得了Ir(PPY)₃主峰位于517nm的发光和主峰位于435nm的蓝色发光.通过分析器件的光谱特性,发现这两个发光峰都是源于SiO₂中加速电子直接碰撞激发有机层引起的固态阴极射线发光.继实现多种有机聚合物材料和有机小分子材料八羟基喹啉铝(Alq₃)的固体阴极射线发光之后,又证实了有机 关键词： 夹层结构器件 有机磷光材料 固态阴极射线发光     

Effects of NPB anode buffer layer on charge collection in ZnO/MEH-PPV hybrid solar cells

We investigate the effects of （N,N’-diphenyl）-N,N’-bis（1-naphthyl）-1,1’-biphenyl-4,4’-diamine （NPB） buffer layers on charge collection in inverted ZnO/MEH-PPV hybrid devices. The insertion of a 3-nm NPB thin layer enhances the efficiency of charge collection by improving charge transport and reducing the interface energy barrier, resulting in better device performances. S-shaped light J–V curve appears when the thickness of the NPB layer reaches 25 nm, which is induced by the inefficient charge extraction from MEH-PPV to Ag. Capacitance–voltage measurements are performed to further investigate the influence of the NPB layer on charge collection from both simulations and experiments.     

利用Ag_2O/PEDOT:PSS复合缓冲层提高P3HT:PCBM聚合物太阳能电池器件性能的研究

利用Ag2O/PEDOT:PSS(聚(3,4-乙撑二氧噻吩):聚苯乙烯磺酸盐)作为复合阳极缓冲层,制备了P3HT:PCBM(聚(3-已基噻吩):富勒烯衍生物)聚合物太阳能电池器件,并通过改变氧化银插入层的厚度来分析复合缓冲层对器件性能的影响.实验发现,具有阳极缓冲层修饰的器件在退火处理后,光伏性能得到了改善.相比于单一PEDOT:PSS缓冲层的器件,Ag2O/PEDOT:PSS复合缓冲层可以增大器件的短路电流密度和外量子效率,使器件效率得到提高.分析表明,退火处理可以有效改善活性层的薄膜形貌,增加光的吸收和激子的解离,而较薄氧化银的引入,可以有效降低阳极处空穴的输运势垒,提高器件空穴收集效率,并能充当化学间隔层,提高器件光伏性能和稳定性.