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Using pulsed laser with different wavelengths, transient photovoltage (TPV) is investigated for the sandwich device of indium tin oxide (ITO)/poly (2-methoxy-5-(2′-ethylhexyloxy)-1, 4-phenylenevinylene) (MEH-PPV) (500 nm)/Al. At laser wavelength of 500 nm, a 0.1 millisecond negative TPV signal appears followed by a positive one lasting 40-80 milliseconds. With increasing laser wavelength, the negative signal becomes weak and disappears when wavelengths λ?560 nm. This work demonstrates the process of exciton dissociation at the interface between ITO and MEH-PPV. A new method measuring the relative dissociation rate at the interface between polymer and electrode is introduced. It is estimated that the dissociation rate at Al interface is 4-8 times of that at the ITO interface. 相似文献
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WU Bo LI WenBin YU HaoMiao YOU YinTao CHEN XiaoQing HE Yun HOU XiaoYuan 《中国科学:物理学 力学 天文学(英文版)》2013,56(10):2012-2015
Transient photovoltage of ITO/organic/Al cells is studied under different bias polarities and voltages.It is found that for an ITO/NPB/Al cell,light incidence on the Al side induces more bias-dependent transient photovoltage variation when the photovoltage is positive than when it is negative.However,for an ITO/C60 /Al cell,the variation characteristics of transient photovoltage is reversed.These results support the previously proposed mechanism that Al could inject charges into the organic layer upon photon excitation,indicating that the absorption of electrode can also contribute to photovoltaic effect. 相似文献
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De-Li LiWei Si Wen-Chao YangYao Yao Xiao-Yuan HouChang-Qin Wu 《Physics letters. A》2012,376(4):227-230
The effect of exciton interfacial dissociation on transient photocurrent (TPC) in a single-layer organic solar cell is investigated within a time-dependent device model. The spike observed in TPC experiments is attributed to exciton dissociation at the electrode/organic interface. In comparison with the observed negative signal of transient photovoltage (TPV), the spike more directly reflects the charge processes at the interface. Moreover, numerical results show that the spike of TPC is sensitive to the voltage applied on the device and the hole mobility of the organic semiconductor. Further investigation on the spike by the favorable TPC technique is suggested to provide details about the exciton and carrier processes at the interface. 相似文献
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LI WenBin SONG QunLiang SUN XiaoYu WANG MeiLiang WU HuanRong DING XunMin & HOU XiaoYuan Surface Physics Laboratory Fudan University Shanghai China 《中国科学:物理学 力学 天文学(英文版)》2010,(2)
This paper presents an overview of the recent progress of small molecule organic solar cells mainly based on the previous worksof our group. We will mainly focus on the interfacial processes in the cells. The dissociation of excitons at electrode/organic andorganic/organic interfaces can be directly observed by transient photovoltage measurements. A simple model including dissociationof excitons at the interface and drift of free carriers in the built-in field is proposed to explain the observed signals of ... 相似文献
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合成了一种新型的稀土铽配合物材料Tb(o-MBA)3phen,并把它作为发光材料应用于有机电致发光器件中。将铽配合物与PVK的混合溶液用旋涂法制得发光层,并利用Alq3作为电子传输层制备了多种结构的电致发光器件:器件A:ITO/PVK:Tb(o-MBA)3phen/LiF/Al;器件B:ITO/PVK:Tb(o-MBA)3phen/BCP/Alq3/LiF/Al;器件C:ITO/BCP/PVK:Tb(o-MBA)3phen/Alq3/LiF/Al。由器件A和C得到了纯正的、明亮的Tb3+的绿光发射,发射光谱中四个特征峰分别对应着能级5D4→7FJ(J=6,5,4,3)的跃迁,而PVK的发光完全被抑制。在光致发光中PVK的发射光谱和铽配合物的激发光谱有一定的重叠,两者之间可能存在Frster能量传递。同时PVK与铽配合物掺杂体系的激发光谱与纯PVK的激发光谱非常相像,而与铽配合物的激发光谱差别很大,这也说明掺杂体系中铽的发光有一部分来源于PVK分子的激发,PVK与铽配合物之间存能量传递过程。研究了掺杂体系的电致发光性能,在电致发光中,铽的发光主要来源于稀土配合物直接俘获载流子形成激子并复合发光。通过优化选择得到了发光性能较好的器件,器件的最大亮度在17V时达到180cd/m2。 相似文献
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Experimental in situ photoluminescence and transient photovoltage results show that the interface formed by N, N{'}-Bis(naphthalene-1-yl)-N, N{'}-bis(phenyl) benzidine (NPB) and tris(8-hydroxyquinoline) aluminum (Alq{3}) acts as an exciton dissociation site. Because of this dissociation effect, excitons formed in NPB at or within a diffusion length of the interface tend to dissociate before they radiatively decay to generate blue light. This suggests that the action of the "hole-blocking layer" used in indium tin oxide\NPB\hole-blocking layer\Alq{3}\aluminium to promote blue light emission from the NPB is more "exciton dissociation inhibition" than "hole blocking." 相似文献
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Well-aligned ZnO nanorod array, synthesized by wet chemical bath deposition (CBD) method on conductive indium-in-oxide (ITO) substrate, was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. Surface photovoltage (SPV) technique based on a scanning Kelvin Probe system was employed to investigate the optoelectronic behavior of ZnO nanorod array. The surface photovoltage and its time-resolved evolution process are used to determine the energy level structure of the ZnO nanorod array. 相似文献
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报道了Al/α-SnPc/ITO夹心结构的瞬态光电压随入射光强度和波长变化的演变特性和稳态连续光照射下的光电压作用光谱。稳态光电压作用光谱和其对应吸收光谱的变化趋势非常接近;而瞬态光电压的大小、极性和响应时间则共同取决于入射光的强度和波长。其中瞬态光电压的正峰部分(相对于ITO电极)只在较强的光照射下才出现,而且其响应时间也总是慢于同一条件下出现的负电压峰。文中对该现象的内在机制作了初步的探讨。 相似文献
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Berke K Tongay S McCarthy MA Rinzler AG Appleton BR Hebard AF 《J Phys Condens Matter》2012,24(25):255802
We investigate the electronic transport properties across the pentacene/graphene interface. Current transport across the pentacene/graphene interface is found to be strikingly different from transport across pentacene/HOPG and pentacene/Cu interfaces. At low voltages, diodes using graphene as a bottom electrode display Poole–Frenkel emission, while diodes with HOPG and Cu electrodes are dominated by thermionic emission. At high voltages conduction is dominated by Poole–Frenkel emission for all three junctions. We propose that current across these interfaces can be accurately modeled by a combination of thermionic and Poole–Frenkel emission. Results presented not only suggest that graphene provides low resistive contacts to pentacene where a flat-laying orientation of pentacene and transparent metal electrodes are desired but also provides further understanding of the physics at the organic semiconductor/graphene interface. 相似文献
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Juan de Dios Ruiz Juan Hinojosa Alejandro Alvarez-Melcon 《Applied Physics A: Materials Science & Processing》2013,110(2):263-267
Two kinds of inorganic/organic hybrid junctions based on ZnO nanorods (NRs), i.e. two-layer planar heterojunction and embedded bulk composite structures, were fabricated on ITO glass substrates. Surface photovoltage (SPV) methods based on a Kelvin probe and a lock-in amplifier were respectively utilized to study the photogenerated charges at the surface and the interface in the ZnO-based hybrid junctions. Results indicate that the lock-in SPV response of the bulk composite structure is much higher than its planar counterpart in terms of intensity and spectral range. Therefore, ZnO NR/PF (poly(9,9-di-n-octylfluorenyl-2,7-diyl)) embedded bulk composite structures are more suitable and preferred for photovoltaic application. 相似文献
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从三线态激子的发光机理入手,研究了PBD作为电子传输材料对PVK:Ir(ppy)3体系的影响。实验中制备了单层器件ITO/PVK:Ir(ppy)3/PBD/Al,ITO/PVK:Ir(ppy)3:PBD/Al和双层器件,ITO/PVK:Ir(ppy)3:PBD/BCP/Al,其中PVK:Ir(ppy)3的掺杂浓度比例不变,通过改变PBD的掺杂浓度,其变化范围是PBD与PVK的质量比从0:100到20:100,制得了一系列器件,研究了它们的光致发光(PL)光谱和电致发光(EL)光谱。发现PBD这种电子传输材料的加入对器件的亮度有很大提高,当PBD与PVK质量比为10%时,器件亮度最大。 相似文献
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《Current Applied Physics》2020,20(5):648-652
The transient photocurrent (TPC) technique was performed to explore the dynamics of excitons and carriers at organic active layer/buffer layer interfaces. A special device with ITO/PEIE/NPB/C60/Al structure was designed to study the interfacial processes at the NPB/C60 interface. An external electrical field was provided to neutralize the built-in electrical field of the device. Interestingly, a new phenomenon was observed, wherein the polarity of the TPC changed from negative to positive under an external electrical field. The initial negative signal was ascribed to exciton separation by the built-in field in C60, and the subsequent positive signal can be attributed to the diffusion of electrons that accumulate at the NPB/C60 interface. TPC measurements shown that further increasing the external electrical field causes polarity to change twice. Analyzing the two changes in polarity revealed that the NPB did not only extract holes from C60 but also provided an effective interface for exciton dissociation. 相似文献
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本文基于Forouhi-Bloomer 模型得到了这种功能层的光学常数.根据菲涅耳系数矩阵法计算了这种器件内的光电场分布,并计算了不同厚度的聚合物功能层的光子吸收数.同时,通过Onsager-Braun理论,分析了在无外加电场下聚合物功能层厚度对激子分离概率的影响.理论分析和实验结果证明:在特定的薄膜制备工艺下,器件结构为ITO/PEDOT/ P3HT:PC60BM /LiF/Al时,聚合物功能层厚度在100 nm左右时,可以使器件的光子吸收数最大化,同时避免了激子分离概率的降低.
关键词:
光学常数
激子
聚合物太阳能电池 相似文献
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Yoshiaki Sugimoto Nobuhiro Tsumori Shintaro Nomura Toshiharu Saiki 《Optical Review》2009,16(3):269-273
Near-field photoluminescence (PL) imaging spectroscopy was used to investigate multi-exciton and charged-exciton states confined
in a single GaAs interface fluctuation quantum dot. We determined the origin of peaks in the PL spectra by employing a wavefunction
mapping technique. We observed distortion of the exciton wavefunction due to the electric field produced by an excess electron
at a nearby confined state. Near-field wavefunction mapping was demonstrated to be a powerful tool for visualizing the local
environment, which affects the emission properties of quantum dots. 相似文献
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为研究激基复合物器件激子复合区域的变化,在TPD/BPhen界面可形成激基复合物发光的基础上,以Ir(pq)2(acac)为探测层,制备器件ITO/Mo O_3(2.5 nm)/TPD((40-x)nm)/Ir(pq)2(acac)(0.5 nm)/TPD(x,x=0,3,6,10 nm)/BPhen(40 nm)/Cs2CO_3/Al,其中靠近BPhen的TPD称之为间隔层。电致发光光谱表明,该组器件的激子复合区域主要位于Ir(pq)2(acac)薄层和TPD/BPhen界面,分别发射595 nm和478 nm的光。随着TPD间隔层厚度的增加和电压的升高,发光区域向激基复合物区域(TPD/BPhen界面)移动,即更多的电子和空穴在TPD/BPhen界面形成激基复合物发光,Ir(pq)2(acac)发光减弱。当间隔层厚度由0 nm增至10nm时,6 V电压下的Ir(pq)2(acac)和激基复合物发光强度的比值由44降至1.5。对于间隔层厚度为6 nm的器件,Ir(pq)2(acac)和激基复合物发光强度的比值由6 V时的2.8降至10 V时的1.0。由此可见,激基复合物给体作间隔层能有效调节激子复合区域。 相似文献
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The effect of a nm-thick interlayer of copper phthalocyanine (CuPc) or perylene dye (MePTCDI) on currentvoltage characteristics of planar organic systems is discussed in this work. The MePTCDI layer in the ITO/MePTCDI/CuPc/Au system strongly reduces reverse dark current by blocking injection of holes from ITOinto CuPc leading to high values of rectification ratio. The CuPc interlayer in the ITO/CuPc/MePTCDI/Ag system causes a strong reduction in electron injection from ITOand reverses a forward polarity. Modification of current-voltage characteristics of illuminated systems with an interlayer of MePTCDI or CuPc is associated with a strong photovoltaic effect. This results from efficient excition dissociation at the CuPc/MePTCDI interface. Saturation current, determined by this process of charge carrier photogeneration, can be observed at particular voltage polarity. 相似文献
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On textured n-type silicon substrates for solar cell manufacturing, the relation between light trapping behavior, structural
imperfections, energetic distribution of interface state densities and interface recombination losses were investigated by
applying surface sensitive techniques. The field-modulated surface photovoltage (SPV), in-situ photoluminescence (PL) measurements, total hemispherical UV-NIR-reflectance measurements and electron microscopy (SEM) were
employed to yield detailed information on the influence of wet-chemical treatments on preparation induced micro-roughness
and electronic properties of polished and textured silicon substrates. It was shown that isotropic as well as anisotropic
etching of light trapping structures result in high surface micro-roughness and density of interface states. Removing damaged
surface layers in the nm range by wet-chemical treatments, the density of these states and the related interface recombination
loss can be reduced. In-situ PL measurements were applied to optimise HF-treatment times aimed at undamaged, oxide-free and hydrogen-terminated substrate
surfaces as starting material for subsequent solar cell preparations.
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