频控变色场致发光器件及机理研究

吸收是发光的前提条件,吸收变了发光的其他特性也会跟着改变。发光寿命长短又会反过来影响吸收的多少,这不仅存在于光致发光中,而且是一个普遍规律。作者从电场引起的场致发光中发现,在同一种材料中掺入两种发光寿命长短相差悬殊的发光中心Cu,Mn,利用激发电源频率的变化明显地显示出器件发光光谱的变化,在一种材料中实现了变色。实验结果证明提高激发频率可以提高短寿命发光中心的激发效率,通过改变激发频率的大小,就可以在掺有两种发光寿命大小不一的材料中实现了发光颜色的变化,这个规律只与发光中心寿命有关,而与激发方式及猝灭原因无关。     

新型稀土铕配合物Eu(o-BBA)3(phen)电致发光研究

研究了一种新的稀土配合物邻苯甲酰苯甲酸-1,10-菲咯啉-铕(Eu(o-BBA)3(phen))的电致发光特性.采用不同的电子传输层材料,制备了多种结构的有机电致发光器件及有机无机复合器件.比较了单层电致发光器件A:ITO/PVK:Eu/Al与有机无机复合器件B:ITO/PVK:Eu/ZnS/Al发光性能的不同.分析了采用无机半导体材料ZnS作为电子传输层的优点.研究结果表明采用无机的电子传输层,能有效地避免激基复合物的形成,提高器件的亮度同时保持稀土离子发光的色纯性.     

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。     

Influence of small-molecule material on performance of polymer solar cells based on MEH-PPV:PCBM blend

In this work,the influence of a small-molecule material,tris(8-hydroxyquinoline) aluminum (Alq 3),on bulk het-erojunction (BHJ) polymer solar cells (PSCs) is investigated in devices based on the blend of poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and [6,6]-phenyl-C 61-butyric acid methyl ester (PCBM).By dop-ing Alq 3 into MEH-PPV:PCBM solution,the number of MEH-PPV excitons can be effectively increased due to the energy transfer from Alq 3 to MEH-PPV,which probably induces the increase of photocurrent generated by excitons dissociation.However,the low carrier mobility of Alq 3 is detrimental to the efficient charge transport,thereby blocking the charge collection by the respective electrodes.The balance between photon absorption and charge transport in the active layer plays a key role in the performance of PSCs.For the case of 5 wt.% Alq 3 doping,the device performance is deteriorated rather than improved as compared with that of the undoped device.On the other hand,we adopt Alq 3 as a buffer layer instead of commonly used LiF.All the photovoltaic parameters are improved,yielding an 80% increase in power conversion efficiency (PCE) at the optimum thickness (1 nm) as compared with that of the device without any buffer layer.Even for the 5 wt.% Alq 3 doped device,the PCE has a slight enhancement compared with that of the standard device after modification with 1 nm (or 2 nm) thermally evaporated Alq 3.The performance deterioration of Alq 3-doped devices can be explained by the low solubility of Alq 3,which probably deteriorates the bicontinuous D-A network morphology;while the performance improvement of the devices with Alq 3 as a buffer layer is attributed to the increased light harvesting,as well as blocking the hole leakage from MEH-PPV to the aluminum (Al) electrode due to the lower highest occupied molecular orbital (HOMO) level of Alq 3 compared with that of MEH-PPV.     

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.     

The concentration quenching and crystallographic sites of Eu2+ in Ca2BO3Cl

A yellow phosphor, Ca2BO3CI：Eu2＋, is prepared by the high-temperature solid-state method. Under the condition of excitation sources ranging from ultraviolet to visible light, efficient yellow emission can be observed. The emission spectrum shows an asymmetrical single intensive band centred at 573 nm, which corresponds to the 4f65dl→4f7 transition of Eu2＋. Eu2＋ ions occupy two types of Ca2＋ sites in the Ca2BO3C1 lattice and form two corresponding emission centres, respectively, which lead to the asymmetrical emission of Eu2＋ in Ca2BO3C1. The emission intensity of Eu2＋ in Ca2BO3C1 is influenced by the Eu2＋ doping concentration. Concentration quenching is discovered, and its mechanism is verified to be a dipole-dipole interaction. The value of the critical transfer distance is calculated to be 2.166 nm, which is in good agreement with the 2.120 nm value derived from the experimental data.     

从热释光曲线同时确定电子复合与俘获之比及陷阱深度

复合发光的本质是两种载流子的复合,但其衰减规律则视具体情况可以从一个极限(指数)变到另一个极限(抛物线),即复合发光是一个连续变化的过程。这主要取决于导带电子的行为,导带电子的行为可以用电子与离化发光中心复合与被陷阱俘获之比来表示。加热发光是在变化温度下的发光弛豫,它既与复合与俘获之比有关,还是陷阱深度的函数,因此在利用加热发光曲线测定陷阱深度时,要同时确定这两个参数。利用热释光动力学模型及其原理,对其发光过程进行了分析,解释了热释光过程既不是一个单分子过程也不是一个双分子过程,这两个过程实际是两个极端情形,都是近似。文章同时利用一些工具软件具体计算了ZnS:Cu, Co的陷阱深度及电子复合与俘获概率之比,精确的计算了这些参数,得n₀ =2.6, ε=0.86eV。     

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.     

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.     

一维有序ZnO纳米棒阵列的制备与表征

通过改进传统水热法的密闭、高压的条件,在非密闭、常压环境下在氧化铟锡玻璃衬底上自组装生长了取向高度一致并且分散性好的ZnO纳米棒阵列.首先将乙酸锌溶胶旋涂到氧化铟锡玻璃衬底上,经热处理得到致密的ZnO纳米晶薄膜,然后将其垂直放入前驱体溶液中通过化学溶液沉积生长得到ZnO纳米棒阵列.室温条件下,对样品进行了SEM和XRD的测试.表明生成的氧化锌纳米棒阵列沿c轴取向,实现了定向生长,且纳米棒结晶较好,为六方纤锌矿结构,直径约为40 nm,长度达到微米量级.室温下的吸收光谱表明,由此方法得到的纳米棒纯度较高,有强的紫外吸收.室温下,观测到了该有序ZnO纳米棒阵列在387 nm处强的窄带紫外发射,半高宽小于30 nm,在468 nm处还有一强度较弱的蓝光发射峰.