有机体异质结太阳能电池的数值分析

介绍了一种有机体异质结太阳能电池的数值模拟方法,模型使用Onsager提出的成对复合理论,并结合了完善的无机半导体理论而提出来的,其结果与实验结果符合较好,证明了模型的正确性.在此基础上分析了器件的内建电场与工作温度对器件性能的影响,以及影响器件光电流的主要因素. 关键词： 有机太阳能电池 体异质结 数值分析     

Light absorption modeling of ordered bulk heterojunction organic solar cells

Ordered bulk heterojunction organic solar cells are devices that combine the advantages of the planar bilayer and the bulk heterojunction architectures. They offer uninterrupted pathways to electrodes for effective charge collection and an extended Donor–Acceptor interface for efficient exciton dissociation. Additionally, this interface can also be a potential approach to increase photon absorption by light trapping. Light absorption and charge carrier generation of organic nanostructures are studied by means of finite-element modeling for a wide range of structuring widths, periods and heights for poly(3-hexylthiophene):1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C₆₁ (P3HT:PCBM) structures. Results show an increase in light absorption at certain wavelengths in the P3HT region with respect to an equivalent planar bilayer model. This increase can be attributed to two phenomena: for the smallest periods the structures behaves like an effective medium, while for periods of the order of magnitude of the incident light wavelength there is light trapping. The maximum increase in absorption was achieved for a 250 nm-width and 500 nm periodicity structure with a height of 40 nm. Exciton diffusion has also been studied to evaluate the effective amount of absorbed light contributing to photocurrent. In this case, best results correspond to the smallest sizes (1.25–12.5 nm-width) for all the considered heights, achieving an increment in the photocurrent up to more than a factor 6 if compared with that of the reference planar bilayer device. This study can be used to optimize our devices, which are achieved via nanoporous anodic alumina templates.     

Study of a ternary blend system for bulk heterojunction thin film solar cells

In this research, we report a bulk heterojunction(BHJ) solar cell consisting of a ternary blend system. Poly(3-hexylthiophene) P3 HT is used as a donor and [6,6]-phenyl C61-butyric acid methylester(PCBM) plays the role of acceptor whereas vanadyl 2,9,16,23-tetraphenoxy-29 H, 31H-phthalocyanine(VOPc Ph O) is selected as an ambipolar transport material. The materials are selected and assembled in such a fashion that the generated charge carriers could efficiently be transported rightwards within the blend. The organic BHJ solar cells consist of ITO/PEDOT:PSS/ternary BHJ blend/Al structure. The power conversion efficiencies of the ITO/ PEDOT:PSS/P3HT:PCBM/Al and ITO/PEDOT:PSS/P3HT:PCBM:VOPcPhO/Al solar cells are found to be 2.3% and 3.4%, respectively.     

基于AsP/MoS2异质结的偏振光电探测器

线偏振光的探测能力是评价偏振光电探测器件的重要指标。黑砷磷(AsP)是一种较为稳定的平面内各向异性材料,由于其面内结构各向异性,其对线偏振光较为敏感,在偏振探测领域有着重要的应用潜力。本文介绍了一种基于AsP/MoS2的高度偏振敏感光电探测器。由于AsP各向异性的光吸收、MoS2有效的载流子收集和输运能力以及范德华异质结对暗电流的抑制作用,该光电探测器实现了大于300的电流开关比,0.27 A/W的电流光响应度以及2×10^10 Jones的比探测率。更重要的是,此类光电探测器在638 nm波段实现了高达3.06二向色性比的偏振特性。这些实验结果表明AsP/MoS2异质结构在偏振光电探测领域有着广阔的应用前景。     

具有光电倍增的宽光谱三相体异质结有机彩色探测器

实验研究了P3HT：PBDT-TT-F：PCBM三相体异质结活性层光谱拓宽及其材料混合度对探测器光电特性的影响以及陷阱辅助光电倍增的机理.在此基础上,获得了一个覆盖350–750 nm波长范围的彩色探测器.该探测器在-1 V低偏压下红绿蓝三基色的光响应度和外量子效率分别达到了470,381,450 mA/W和93%,89%,121%,比探测率均接近10¹² Jones,且各基色的特性参数最大平均相对偏差均小于20%,同时频率带宽分别达到了5,8,8 kHz.结果表明：在保持二相体异质结薄膜原有微观形貌下,掺入少量光谱拓宽材料可实现活性层吸收光谱的拓宽.利用能级陷阱中电子的辅助作用引入外电路空穴注入,可实现探测器光电倍增.通过调节三相材料的混合度可实现基色间探测能力的均衡性.     

The effect of annealing treatment on the performance of bulk heterojunction solar cells with donor and acceptor different weight ratios

Bulk heterojunction organic solar cells(OSCs) based on the blend of poly(2-methoxy-5(2'-ethyl-hexyloxy)-1,4-phenylenevinylene(MEH-PPV) and [6,6]-phenyl C61 butyric acid methyl ester(PCBM) with different weight ratios(from 1:3 to 1:5) have been fabricated and the effect of annealing treatment on the performance of OSCs has also been studied.Experimental results point to the best optimized doping concentration 1:4 for MEH-PPV:PCBM.Furthermore,it is found that the devices with annealing treatment at 150℃ with ...     

基于MEH-PPV/ZnSe纳米复合器件的电致发光特性的研究

以巯基乙酸作为稳定剂在水相中制备了ZnSe纳米晶,用X射线粉末衍射(XRD)和X射线光电子能谱(XPS)对其进行了表征。用表面活性剂将ZnSe纳米晶从水相中转移到有机相中,使其与聚合物MEH-PPV复合作为发光层,制备了多层电致发光器件Glass/ITO/MEH-PPV∶ZnSe/BCP/Alq₃。对ZnSe纳米晶和MEH-PPV薄膜的光致发光谱及其吸收光谱的比较表明ZnSe纳米晶和MEH-PPV之间存在着能量传递,这是导致纳米复合薄膜的光致发光光谱和电致发光光谱存在差异的原因之一。文章对其在光激发和载流子注入条件下的不同发光机制进行了讨论。通过对器件的光电特性进行研究,发现ZnSe纳米晶发光的比例随着外加电压的增加而增加,而且器件的I-V特性基本上符合二极管的特性。     

掺杂CuPc的MEH-PPV/PCBM有机太阳电池研究

采用旋涂法制备了掺杂铜酞菁(CuPc)的聚(2-甲氧基,5-(2-乙基-乙氧基)-对苯乙炔)(MEH-PPV)/ 富勒烯衍生物(PCBM)有机太阳电池. 测试结果表明:掺杂15% CuPc的MEH-PPV/PCBM太阳电池效率(1.41%)比标准的MEH-PPV/PCBM太阳电池(1.26%)提高12%. 器件的吸收谱和迁移率测试表明CuPc导致的吸收谱增强和迁移率提高是器件效率提高的主要原因. 关键词： 有机太阳电池 CuPc掺杂 MEH-PPV/PCBM器件     

Charge transport in low-concentration MEH-PPV conjugated polymer/fullerene composites

Charge transport was studied in composites of poly[2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylene-vinylene] (MEH-PPV) conjugate polymer and low-concentration fullerenes (C₆₀) below the percolation threshold. The electron mobility showed a linear increase with the fullerene concentration, to which the hole mobility was insensitive. Our results indicate that fullerene–polymer networks provide a conduction path to the electrons, whereas the holes are transported through the polymer-only paths. The microscopic environments of the two distinct conduction paths in the composites as revealed by the electric field dependence of the mobilities are also discussed.     

High-performance self-powered photodetector based on organic/inorganic hybrid van der Waals heterojunction of rubrene/silicon

Organic/inorganic hybrid van der Waals heterostructure with an atomically abrupt interface has attracted great research interests within the field of multifunctional electronic and optoelectronic devices. The integration of organic rubrene films with inorganic Si semiconductors can avoid the atomic mutual-diffusion at the interface, and provide the possibility of forming two-dimensional van der Waals heterojunction accompanied with the type-II energy band alignment, due to the transfer behaviors of majority carriers at the interface. In this study, the high-quality rubrene/Si van der Waals heterostructure with an electronically abrupt junction was prepared, and a self-powered photodetector was then constructed based on this hybrid heterojunction. The photodetector demonstrated an excellent switching response to the 1064 nm monochromatic light with large on/off current ratio of 7.0×10~3, the maximum photocurrent of 14.62 m A, the maximum responsivity of 2.07 A/W, the maximum detectivity of 2.9×10~(11) Jones, and a fast response time of 13.0 μs. This study offers important guidance for preparing high-quality rubrene/Si hybrid van der Waals heterostructure with desirable band alignment, and the designed heterojunction photodetector has an important application prospect in the field of multifunctional optoelectronics.     

ZnSe(ZnS)纳米晶与MEH-PPV的共掺有机电致发光器件

采用水相法合成核壳结构ZnSe/ZnS 纳米晶,经X射线衍射(XRD)分析和透射电子显微镜(TEM)表征,证实所制备的样品为立方晶型闪锌矿结构ZnSe/ZnS量子点。按照一定的质量比将ZnSe/ZnS 纳米晶和有机聚合物MEH-PPV(poly ) 共掺并将其作为发光层,分别制备单层和多层有机电致发光器件,结构为ITO/MEH-PPV∶ZnSe(ZnS)(50 nm)/Al和 ITO/PEDOT∶PSS(70 nm)/ MEH-PPV∶ZnSe(ZnS)(50 nm)/BCP(15 nm)/Alq₃(12 nm) /LiF(0.5 nm)/Al。实验结果表明,多层发光器件的发光特性与单层器件不同,工作电压的增大使其发光峰发生了明显的蓝移。     

Influence of interface modification on the performance of polymer/Bi2S3 nanorods bulk heterojunction solar cells

In this paper, bulk heterojunction photovoltaic devices based on the poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV):Bi₂S₃ nanorods hybrid material were present. To optimize the performance of the devices, the interface modification of the hybrid material that has a significant impact on the exciton dissociation efficiency was studied. An improvement in the device performance was achieved by modifying the Bi₂S₃ surface with a thin dye layer. Moreover, modifying the Bi₂S₃ surface with anthracene-9-carboxylic acid can enhance the performance further. Compared with the solar cells with Bi₂S₃ nanorods hybrid with the MDMO-PPV as the active layer, the anthracene-9-carboxylic acid modified devices are better in performance, with the power conversion efficiency higher by about one order in magnitude.     

MEH-PPV/CdSe纳米复合器件的光电导特性的研究

以CdO和Se粉作为前驱物,在TOPO/TOP有机体系中制备了CdSe纳米晶,将其与聚合物MEH-PPV复合制备了复合光电导器件,研究了它的光电导特性,并将其与单层MEH-PPV光电导器件的特性进行了比较。结果发现纳米复合光电导器件的光电流响应光谱的2个峰的位置基本上与MEH-PPV和CdSe纳米晶的吸收峰的位置相对应,这说明CdSe纳米晶和聚合物MEH-PPV的吸收对光电流都有贡献,主要是由于CdSe纳米晶和MEH-PPV界面处的激子离化和电荷转移造成的。而且复合器件的光电流较单层有所增强,且MEH-PPV器件光谱的响应范围更宽。     

High bandwidth surface-illuminated InGaAs/InP uni-travelling-carrier photodetector

Uni-traveling-carrier photodiodes(UTC-PDs)with ultrafast response and high saturation output are reported.A gradient doping layer and a narrow InP cliff layer were introduced to enhance the saturation and bandwidth characteristics.We measured the dark current,photo response,bandwidth,and saturation current of the fabricated UTC devices.For a15-μm-diameter device,the dark current was 3.5 nA at a reverse bias of 1 V,and the 3-dB bandwidth was 17.2 GHz at a reverse bias of 5 V,which are comparable to the theoretically values.The maximum responsivity at 1.55μm was 0.32 A/W.The saturation output current was over 19.0 mA without bias.     

Effect of CdS modification on photoelectric properties of TiO2/PbS quantum dots bulk heterojunction

TiO₂/PbS(CdS) quantum dots (QDs) bulk heterojunction has been fabricated by successive ionic layer adsorption and reaction method via alternate deposition of PbS and CdS QDs. In comparison with TiO₂/PbS heterojunction, the incident photon to current conversion efficiency was increased almost 50% in the visible region. Meantime, the short-circuit current and open-circuit voltage were enhanced 200% and 35% respectively. The influence mechanism of CdS is related to reduction of trap state density at TiO₂/PbS interface and PbS QDs surface by the discussion of the dark current density–voltage curves, the transient photocurrent response curves and the electrochemical impedance spectra spectroscopy (EIS).     

Improvement in electroluminescence performance of n-ZnO/Ga_2O_3 /p-GaN heterojunction light-emitting diodes

n-ZnO/p-GaN heterojunction light-emitting diodes with and without a Ga2O3 interlayer are fabricated. The electroluminescence （EL） spectrum of the n-ZnO/p-GaN displays a single blue emission at 430 nm originating from GaN, while the n-ZnO/Ga2O3/p-GaN exhibits a broad emission peak from ultraviolet to visible. The broadened EL spectra of n-ZnO/Ga2O3/p-GaN are probably ascribed to the radiative recombination in both the p-GaN and n-ZnO, due to the larger electron barrier （ΔEC=1.85 eV） at n-ZnO/Ga2O3 interface and the much smaller hole barrier （ΔEV=0.20 eV） at Ga2O3/p-GaN interface.     

Binary response Se/ZnO p‐n heterojunction UV photodetector with high on/off ratio and fast speed

A high‐performance UV photodetector (PD) based on a p‐Se/n‐ZnO hybrid structure with large area (more than 1×1 cm) is presented in this study. The device is theoretically equivalent to a parallel‐connection circuit for its special structure and shows multifunction at different voltage bias, which means the output signal can be tailored by an applied voltage. The Se/ZnO PD shows binary response (positive and negative current output under on/off periodical light illumination) under small reverse bias (–0.05 V and –0.1 V) which efficiently reduces the negative effect of noise signal in weak‐signal detection applications. At zero bias, with the aid of a p‐n heterojunction, a high on/off ratio of nearly 10⁴ is achieved by this device at zero set bias under 370 nm (∼0.85 mW cm⁻²) illumination and this on/off ratio can be achieved in 0.5 s. The device also shows a fast speed with rise time of 0.69 ms and decay time of 13.5 ms measured by a pulse laser, much faster than that of a pure ZnO film. The Se/ZnO PD in this research provides a new pathway to fabricate multifunctional high‐speed, high signal‐to‐noise ratio, high detectivity and high selectivity UV photodetectors.

     

A 3D SiC MOSFET with poly-silicon/SiC heterojunction diode

A three-dimensional(3D)silicon-carbide(SiC)trench metal-oxide-semiconductor field-effect transistor(MOSFET)with a heterojunction diode(HJD-TMOS)is proposed and studied in this work.The SiC MOSFET is characterized by an HJD which is partially embedded on one side of the gate.When the device is in the turn-on state,the body parasitic diode can be effectively controlled by the embedded HJD,the switching loss thus decreases for the device.Moreover,a highly-doped P+layer is encircled the gate oxide on the same side as the HJD and under the gate oxide,which is used to lighten the electric field concentration and improve the reliability of gate oxide layer.Physical mechanism for the HJD-TMOS is analyzed.Comparing with the conventional device with the same level of on-resistance,the breakdown voltage of the HJD-TMOS is improved by 23.4%,and the miller charge and the switching loss decrease by 43.2%and 48.6%,respectively.     

PbS colloidal quantum dot/ZnO‐based bulk‐heterojunction solar cells with high stability under continuous light soaking

PbS colloidal quantum dot (CQD)‐based depleted bulk‐heterojunction solar cells were constructed, using the 1.2 μm thick nanowire array infiltrated with PbS QDs bearing Br ligands. The long‐term stability tests were performed on the solar cells without encapsulation in air under continuous light soaking using a Xe lamp with an AM1.5G filter (100 mW cm^?2). Time course of solar cell performances during the tests showed two time periods with distinct behavior, that is, the initial transient time period and the relatively stable region following it. The power conversion efficiency was found to keep approximately 90% of the initial value at the end of the 3000 h light soaking test. The stability tests suggest that the PbS surface modification or passivation reactions play an important role in achieving such a high stability, and demonstrate that PbS CQD/ZnO nanowire array‐based depleted bulk‐heterojunction solar cells are highly stable. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Effects of molecular weight and polydispersity of poly (3-hexylthiophene) in bulk heterojunction polymer solar cells

This paper reports the effect of the molecular weight (MW) and polydispersity (PD) of poly (3-hexylthiophene) (P3HT) in bulk heterojunction polymer solar cells (BHJ-SCs). The P3HT with low MW and broad PD exhibited higher crystallinity compared to that with high MW and narrow PD. Due to the improved crystallinity, the BHJ-SCs based on P3HT with low MW and broad PD showed performance with a power conversion efficiency of 3.8% with short-circuit currents of −9.90 mA/cm².