Synthesis,Photophysical, Electrochemical and Thermal Investigation of Anthracene Doped 2-Naphthol Luminophors and their Thin Films for Optoelectronic Devices

A series of novel luminophors of 2-naphthol by doping anthracene were prepared using conventional solid state reaction technique. The photophysical, electrochemical and thermal properties were studied by Fluorescence spectroscopy, XRD, SEM, TGA-DSC and by Cyclic Voltammetry techniques. The thin films were characterized by Fluorescence spectroscopy. XRD study of fine grained powders exhibited sharp peaks which specify crystallinity and homogeneity of the doped luminophors. The fluorescence spectra of doped 2-naphthol exhibited emission of anthracene at 413 nm i.e. blue emission with instantaneous fluorescence quenching of 2-NP due to excitation energy transfer (EET). Electrochemical data specify that the HOMO and LUMO energy levels of the synthesized luminophors are in the range of 5.55–5.71 eV and 3.03–3.24 eV, respectively. TGA-DSC study confirmed thermal stability of prepared luminophors. Hence, overall study proposes that these luminophors seems applicable to be used as n-type materials for Optoelectronic devices.     

Studies on Structural,Optical, Thermal and Electrical Properties of Perylene-Doped p-terphenyl Luminophors

A simple solid state reaction technique was employed for the preparation of polycrystalline luminophors of p-terphenyl containing different amounts of perylene followed by spectral characterization techniques viz. XRD, SEM, TGA-DSC, UV–Visible spectroscopy, thermo-electrical conductivity, fluorescence spectroscopy, fluorescence life time spectroscopy and temperature dependent fluorescence. X-ray diffraction profiles of the doped p-terphenyl reveal well-defined and sharp peaks indicate homogeneity and crystallinity. The SEM micrograph of pure p-terphenyl exhibit flakes like grains and then compact and finally gets separately with perylene amounts. The observed results indicate that closed packed crystal structures of doped p-terphenyl during crystal formation. The band gaps estimated from UV–visible spectroscopy decreased from 5.20 to 4.10 eV, while thermo-electrical conductivity increases with perylene content. The fluorescence spectra showed partial quenching of p-terphenyl fluorescence and simultaneously sensitization of perylene fluorescence at the excitation wavelength of p-terphenyl (290 nm) due to excitation energy transfer from p-terphenyl to perylene. The observed sensitization results are in harmony with intense blue color seen in fluorescence microscopy images and has high demand in scintillation process.     

掺Perylene的PVK薄膜荧光谱及发光机理

用高荧光效率的有机染料芘(perylene)掺杂聚乙烯咔唑(PVK),其荧光光谱与芘的发射光谱基本一致,而且亮度比纯芘发光提高十多倍,说明发光主要来自芘分子,并在PVK和perylene之间存在十分有效的能量传递或电荷转移过程,荧光谱强度随掺杂浓度的变化关系说明存在一个最佳的掺杂浓度比.分析PVK和perylene之间可能发生的能量转移过程,认为从PVK到perylene这种能量转移与实验不符;分析PVK和perylene薄膜的光致发光过程,认为从(PVK+)→(perylene+)和从(PVK-)→(p     

用荧光法研究茶叶防癌抗癌的效用

近年来,由于保健医疗的兴起,有关茶叶防癌的研究受到了极大的关注.美国迈阿密大学一位教授曾周游世界并研究各个地区的茶叶,他发现中国的茶叶是最好的保健饮料,所以这位教授建议饮用中国茶.     

Enhancement of photoluminescence emission intensity of zirconia thin films via aluminum doping for the application of solid state lighting in light emitting diode

Al doped ZrO₂ thin films were deposited on quartz substrates by sol–gel dip coating technique. X-ray diffraction pattern showed the deterioration of the crystallinity of the films with increase in Al doping concentration due to the formation of stress in the film. Scanning electron microscope images showed crack free surface. An average transmittance of >80% (in UV–vis region) was observed for all samples. Optical band gap was found to vary as a function of doping concentration. Photoluminescence spectra of the films exhibited an increase in the emission intensity with increase in Al doping concentration which is due to the increase in oxygen vacancies in the Al doped films. The “Blueshift” and “Redshift” of the PL spectra with increase in Al concentration originates from the change of stress in the films. The enhancement of PL intensity in the Al doped ZrO₂ thin films make it suitable for generation of solid state lighting in light emitting diode.     

掺杂聚合物薄膜的蓝色电致发光

有机薄膜电致发光(OTFEL)自从Tangu[1,2],发表了高效、高亮度的双层结构器件以来,因其驱动电压低、直流驱动、亮度高、效率高、可制成大面积的平板显示而成为当前发光器件研究的热点.但由于有机膜的稳定性差,因此人们逐渐把注意力转向具有稳定结构的聚合物.     

Excimer emission from evaporated pyrene films

Emission spectra and decay times of fluorescence of pyrene thin films prepared by evaporation onto glass substrate at low temperatures were measured. The band positions of the excimer emission from the films evaporated onto substrates at temperatures below about 200 K, are found to the lower energy side of those of the crystal. The decay time of excimer emission in a film prepared by evaporation onto a substrate cooled with liquid nitrogen is about 100 ns at 85 K and is shorter than that of the crystal. These results are discussed in relation to an amorphous structure in the pyrene evaporated thin films. The energy transfer was also studied in evaporated pyrene films containing perylene as a dopant. The results are explained in terms of excimer exciton diffusion through the crystalline structure in the film.     

掺杂PVK薄膜的荧光谱及电荷转移

根据PVK掺杂后荧光谱的变化，说明掺杂PVK薄膜的电致发光存在着从基质分子向掺杂分子的能量传递，用一个由单链模型扩展到包括杂质的哈密顿量进行数值求解，结果表明：在PVK和杂质分子之间有效的能量传递是源于它僮之间的电荷转移，且随着杂质浓度的变化，其荧光谱峰位的移动与掺杂前后系统总能量的改变及荧光谱强度与掺杂后转移的电荷数之间分别存在对应关系。该模型较好地解释了有关的实验结果。     

Al掺杂原子分数及退火温度对ZnO薄膜光学特性的影响

 采用溶胶凝胶法在（0001）Al₂O₃衬底上制备了不同掺杂原子分数的ZnO:Al薄膜,在Ar气氛中进行了600～950 ℃不同温度的退火处理,研究了掺杂原子分数和退火温度对薄膜光致发光、光吸收和透射的影响。结果显示,薄膜的紫外峰强度随掺杂原子分数和退火温度的提高而增强,与缺陷相关的绿光强度却随着掺杂原子分数和退火温度的提高而降低;薄膜光学带隙随掺杂原子分数的提高从3.21 eV增大到3.25 eV;光吸收在可见光区随着退火温度的升高而增大,在紫外区却随着退火温度的升高而减小,透射与吸收的变化规律相反;薄膜吸收边随退火温度的升高出现轻微的红移。     

Effects of doping concentration on properties of Mn-doped ZnO thin films

This paper reports that the radio frequency magnetron sputtering is used to fabricate ZnO and Mn-doped ZnO thin films on glass substrates at 500~°C. The Mn-doped ZnO thin films present wurtzite structure of ZnO and have a smoother surface, better conductivity but no ferromagnetism. The x-ray photoelectron spectroscopy results show that the binding energy of Mn_2p3 / 2 increases with increasing Mn content slightly, and the state of Mn in the Mn-doped ZnO thin films is divalent. The chemisorbed oxygen in the Mn-doped ZnO thin films increases with increasing Mn doping concentration. The photoluminescence spectra of ZnO and Mn-doped ZnO thin films have a similar ultraviolet emission. The yellow green emissions of 4~wt.% and 10~wt.% Mn-doped thin films are quenched, whereas the yellow green emission occurs because of abundant oxygen vacancies in the Mn-doped ZnO thin films after 20~wt.% Mn doping. Compared with pure ZnO thin film, the bandgap of the Mn-doped ZnO thin films increases with increasing Mn content.     

对NFDA1和芘荧光猝灭性质的比较研究

对Bei和芘在电子给体化合物,N,N－二甲苯胺（DMA）和电子受体化合物对苯二甲酸二甲酯（DMTP）作用下的荧光猝灭进行了研究。结果表明芘与DMA和DMTP在室温下均可形成激基化合物（exciplex),而Ben仅仅与DMA形成exciplex。荧光猝灭的数据符合Stern-Volmer方程：F0／F＝1＋KSV[Q],芘的Stern-Volmer常数KSV大于Bei.Bei和芘在荧光猝灭方面的差别是由于Bei分子并不是一个典型的大共轭体系,分子的共平面性不如芘那样典型。     

溶胶-凝胶法制备MgxZn1-xO薄膜的结构及光学特性

用溶胶-凝胶法制备了一系列的Mg_xZn_1-xO(0≤x≤0.3)薄膜,并用X射线衍射(XRD)和光致发光(PL)研究了不同的退火温度和Mg的掺杂含量对Mg_xZn_1-xO薄膜的结构和光学性质的影响.研究表明:Mg_xZn_1-xO薄膜为单相六角纤锌矿结构,并且具有沿c轴的择优取向;发现了中间热处理温度为350℃的Mg_xZn_1-xO薄膜退火温度的转折点为700℃,低于这个温度时随退火温度的升高,(002)衍射峰强度增强且掺Mg的薄膜既有紫外光又有绿光发射;800℃退火时,薄膜的(002)衍射峰强度减小,出现了(100)和(101)衍射峰,且掺Mg的薄膜只有紫外发光峰.不同的掺杂浓度对于发光也有影响,低于700℃退火时,ZnO薄膜只出现紫外发光峰,掺Mg的薄膜却出现了紫外和绿光两个发光峰.     

磁控溅射制备ZnO薄膜的受激发射特性的研究

用射频磁控反应溅射法在二氧化硅衬底上制备ZnO薄膜。得到了在不同温度下ZnO薄膜的吸收与光致发光。观测到了纵光学波 (LO)声子吸收峰与自由激子吸收峰 ;室温 (30 0K)下 ,PL谱中仅有自由激子发光峰。这些结果证实了ZnO薄膜具有较高的质量。探讨了变温ZnO薄膜的发光特性。研究了ZnO薄膜的受激发射特性。     

ZnO：V薄膜后退火处理前后的微结构与发光特性

利用溶胶-凝胶(Sol-gel)法在单晶硅(100)衬底上分别制备了ZnO:V薄膜和纯ZnO薄膜。为进一步研究后退火对ZnO:V薄膜结构和发光性质的影响,在两段式快速退火后又在800℃下进行了后退火处理。X射线衍射的结果表明:后退火处理前,钒(V)的掺入使ZnO结晶质量变差,而800℃退火处理后,从ZnO的衍射峰中可以看出,相对于无V杂样品其结晶质量变好。扫描电子显微镜形貌图中可以看出制备的样品薄膜颗粒大小均匀,薄膜致密度较高。光致发光(PL)谱的研究表明:ZnO:V薄膜在800℃退火处理后,紫外和绿带发光峰均增强,但紫外发光峰增强得更多;与同样条件下制备的纯ZnO薄膜的PL谱比较,发现V掺杂后样品的紫外激子复合发光峰的强度明显增强且峰位发生蓝移,而缺陷引起的绿带发光峰的强度降低。     

退火温度对Cu:ZnO薄膜绿光发射的影响

利用溶胶-凝胶法在Si衬底上制备了不同退火温度的Cu:ZnO薄膜.利用X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜和光致发光谱研究了样品的晶格结构、表面形貌、成分及其发光特性.结果表明:所有样品均具有高度的c轴择优取向,随着退火温度的升高,样品的结晶质量变好,样品的表面都被晶粒覆盖,强而稳定的绿光发射被观察到.绿光强度随退火温度的升高先增加后减小,发光中心位置不随退火温度的变化而改变,这样的绿光发射强而稳定.XRD和XPS结果表明,随退火温度的升高Cu2+还原为Cu+,导致Cu:ZnO薄膜形成的缺陷是VZn,所以绿光发射是由VZn引起的.Cu2+还原为Cu+时,Cu:ZnO薄膜中VZn浓度增加,使绿光发射强度增大.当退火温度超过800?C时,Cu2+的还原能力变差,绿光发射强度减弱.     

TADF激基复合物主体材料提升溶液法制备蓝色荧光有机发光二极管的效率

为了提升溶液法制备的蓝色荧光有机发光二极管(OLEDs)的效率,采用了基于热激活延迟发光(TADF)的激基复合物作为主体材料。TADF激基复合物主体可以利用反向系间窜跃上转换形成单线态激子并将能量传递到客体,从而可以同时利用发光层中的三线态激子和单线态激子,以提升蓝色荧光器件的效率。选择蓝色荧光材料1-4-Di-[4-(N,N-diphenyl)amino]styryl-benzene(DSA-ph)作为客体发光材料,4,4′,4″-T-ris(carbazol-9-yl)triphenylamine(TCTA)掺杂1,3,5-Tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)(TPBi)作为热激活延迟荧光激基复合物主体,通过溶液法制备了蓝色荧光OLEDs。通过测试TCTA,TPBi以及TCTA掺杂TPBi的光致发光光谱发现,与TCTA和TPBi相比,TCTA掺杂TPBi的光致发光谱(PL)发生了明显的红移(峰值波长变为437 nm),而且光谱变宽,证明了TCTA∶TPBi激基复合物的形成。通过对于DSA-ph掺杂激基复合物主体的薄膜与DSA-ph掺杂poly(methyl methacrylate)(PMMA)的薄膜进行PL测试发现,两者发光峰相同,都是来自DSA-ph的发光,说明激基复合物主体将能量传递到了DSA-ph;DSA-ph的吸收光谱与激基复合物主体的PL光谱存在很大重叠,说明激基复合物主体与DSA-ph的能量传递非常有效;通过对激基复合物主体掺杂不同浓度客体的薄膜进行瞬态PL衰减测试发现,与纯DSA-ph的寿命相比,DSA-ph掺杂激基复合物主体之后其寿命会延长,纯DSA-ph的寿命只有1.19 ns,DSA-ph掺杂激基复合物主体的荧光衰减曲线与激基复合物主体的荧光衰减曲线相似,这进一步证明了激基复合物主体将能量传递到了DSA-ph。研究了主体引入以及DSA-ph掺杂浓度对器件性能的影响。对于器件的亮度、电流密度、电压、电流效率、电致发光光谱等参数进行了测试,与不采用激基复合物主体的器件相比,采用激基复合物主体的器件性能明显改善,在DSA-ph掺杂浓度为10%时,器件亮度从2133.6 cd·m^-2提升到了3597.6 cd·m^-2,器件效率从1.44 cd·A-1提升到了3.15 cd·A-1,发光峰只有来自DSA-ph的发光。采用TADF激基复合物主体的方法有潜力实现溶液法制备的高效蓝色荧光OLEDs。     

ZnO薄膜受激发射特性的研究

氧化锌薄膜因其大的激子结合能和强的光发射、激光阈值低和能在高温下工作等优点而成为制备短波长激光、发光二极管等光电子器件的有希望材料。采用激光分子束外延 (L MBE)方法制备了ZnO薄膜。在室温下 ,测量了样品的吸收光谱 ,以及不同光泵浦强度下的发射光谱。从光谱图中可以看出该材料有很好的质量。研究了ZnO薄膜的受激发射特性及机理 ;测量了发射光强与泵浦光强之间的关系 ;比较了较高激发密度下的受激发射、自发发射和激光脉冲的时间特性 ,这些都证实了该发射是受激发射。     

CVD两步法生长ZnO薄膜及其光致发光特性

用CVD两步法在常压下于p型Si(100)衬底上沉积出具有较好择优取向的多晶ZnO薄膜。在325nm波长的光激发下,室温下可观察到显著的紫外光发射(峰值波长381nm)。高温退火后氧空位缺陷浓度增加,出现了一个450~600nm的绿光发光带,发光峰值在510nm。作为比较,用一步法生长的ZnO薄膜结晶质量稍差。在其PL谱中不仅有峰值波长389nm的紫外发射而且还出现了一个很强的蓝光发光中心(峰值波长437nm),退火后同样产生绿光发光带。对这两种绿光发光带的发光机制进行了研究,认为前者源于VO,而后者与O_Zn有密切的关系。     

退火温度对高分子薄膜中掺杂小分子的结晶和光谱学响应特性的影响

研究了小分子材料苝(EPPTC)在高分子材料聚芴衍生物(F8BT)薄膜中的结晶特性随温度的变化规律,以及由此引起的两种材料构成的异质结中激发复合体荧光发射特性的变化。实验结果表明,退火温度的升高会加强小分子与高分子材料在固体薄膜中的相分离。而小分子相在析出过程中,会在分子间作用力诱导下发生π—π团聚而结晶。晶体的尺度在达到小分子材料相变温度之前基本上随温度升高而增大。这一过程将破坏异质结结构,减小小分子与高分子间的接触面积,从而降低激发复合体的形成及其荧光发射强度。同时,由高分子向小分子发生的能量转移过程被显著减弱,而小分子晶相的荧光发射成分提高。这对于调控有机半导体异质结结构,进而改善光伏器件性能具有重要意义。     

Combinatorial thin film sputtering investigation of cerium concentration in Lu2SiO5 scintillators

Lutetium oxyorthosilicate (LSO) thin films with a cerium thickness gradient were sputter deposited to investigate the optimum cerium concentration for emission intensity. Thin film cerium concentration ranged from 0.06 to 0.88 at%. To compare the thin film samples to single crystal LSO, a set of single crystal LSO samples were investigated with cerium concentrations of 0.0015, 0.0095 and 0.078 at%. The thin film samples showed peak photoluminescence emission intensity at a cerium concentration of 0.35 at%; however, the single crystal samples exhibited peak photoluminescence emission intensity at a lower cerium concentration of 0.0095 at%. The photoluminescence excitation and emission spectra as a function of concentration demonstrate the concentration quenching behavior and the mechanisms are speculated to be due to radiative (self-absorption) and non-radiative energy transfer, which may be phonon assisted.