Stably dispersible P3HT/ZnO nanocomposites with tunable luminescence by in-situ hydrolysis and copolymerization of zinc methacrylate

In this paper, the copolymer shell with the internal hydrophobic polymethacrylate layer and the external hydrophilic poly(ethylene glycol) methyl ether groups was successfully bonded on the surface of ZnO nanocrystals through a simple sol–gel method, i.e., radical polymerization of zinc methacrylate (Zn(MA)₂) and poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) and hydrolysis. The prepared ZnO@poly(methacrylate-co-poly(ethylene glycol) methyl ether methacrylate) (ZnO@PPEGMA) nanocrystals showed good dispersion and smaller particle size, due to the presence of copolymer shell. The optical properties of ZnO@PPEGMA nanocrystals were characterized by ultraviolet–visible (UV–vis) spectroscopy and photoluminescence (PL) spectroscopy. The results indicated that the absorption edge and PL emission in the UV region of ZnO@PPEGMA nanocrystals appeared obvious blue-shift, due to the smaller particle size. Incorporation of ZnO@PPEGMA nanocrystals into poly(3-hexylthiophene) (P3HT) matrix, the dispersion of P3HT/ZnO@PPEGMA nanocomposites was greatly improved and the nanocomposites possessed excellent photoluminescence stability. Meanwhile, it was observed that the PL emission of P3HT/ZnO@PPEGMA nanocomposites was enhanced significantly, due to the presence of copolymer shell and the improvement of compatibility of ZnO@PPEGMA in the P3HT matrix. The results showed that the P3HT/ZnO@PPEGMA nanocomposites could be potential candidates for optical applications.     

Magnetic properties of poly(3-hexylthiophene)

A room temperature ferromagnetic phase is observed in samples of poly(3-hexylthiophene) partially doped with ClO₄⁻. The magnetic behavior presents a strong dependence on the sample preparation conditions, in particular, a dependence with the final potential of the sample after reduction. The origin of the ferromagnetism is proposed to be associated with interactions between spin 1/2 polarons formed in the polymeric chain upon doping. The dependence of saturation and spontaneous magnetization as the function of the final potential after reduction shows a way to control the magnetic properties of this polymer.     

Organic magnetoresistance and spin diffusion in organic semiconductor thin film devices

We review recent work in the field of organic spintronics, focusing on our own contributions to this field. There are two principle magnetoresistance effects that occur in organic devices. (i) Organic magnetoresistance (OMAR), which occurs in nonmagnetic organic semiconductor devices. For example, in devices made from the prototypical small molecule Alq₃ OMAR reaches values of 10% or more at room temperature. (ii) Organic spin‐valve effects that occur in devices that employ ferromagnetic electrodes for spin‐polarized current injection and detection. We undertake an analysis of these two types of magnetoresistance with the goal of identifying the dominant spin‐scattering mechanism. Analysis of OMAR reveals that hyperfine coupling is the dominant spin‐coupling mechanism. Spin–orbit coupling, on the other hand, is important only in organic semiconductor materials containing heavy atoms. We explore the reasons why spin–orbit coupling is relatively unimportant in hydrocarbon materials. Next, we present a theory for spin diffusion in disordered organic semiconductors based on hyperfine coupling, taking into account a combination of incoherent carrier hopping and coherent spin precession in the random hyperfine magnetic fields. We compare our findings with experimental values for the spin‐diffusion length. Finally, we demonstrate a criterion that allows the determination whether the organic spin‐valves operate in the tunneling or injection regimes. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electrical properties of nanointerface at poly(3-hexylthiophehe) and metal junctions probed directly with potential tip

Electrical properties at the nanointerfaces of head-to-tail coupled poly(3-hexylthiophene), PHT and metals (Au, Al) in sandwich type Al/PHT/Au diodes have been investigated using a nanomanipulator with the potential probing tip. It has been directly found that the highly insulating layer and the appreciable contact resistance are formed at Al/PHT with the thickness of several tens nanometer and PAT/Au, respectively. The bias dependence of the interface resistances at Al/PHT shows the origin of rectification. It has also been found that the interface resistance at PAT/Au is unexpectedly large, though the current–voltage behavior is ohmic. The results indicate the contact resistances between PHT and metals at the nanometric region are important factors to determine the diode performance.     

高分子有机场效应晶体管中半导体薄膜结晶行为及微观结构变化的研究

为了探索高分子有机场效应晶体管(OFET)中高分子自组织机理与电荷传输的关联性,采用同步辐射掠入射X射线衍射技术研究了高分子OFET中以高度区域规则的聚(3-己基噻吩)(RR-P3HT)为代表的半导体层的结晶行为及微观结构组织变化,及其引起的高分子半导体电荷传输机理.研究发现,采用自组装单分子层(SAMs)技术进行界面修饰,可以完善绝缘层与RR-P3HT半导体层之间的界面效果.SAMs的形成改善了界面,可以有效地控制上层RR-P3HT半导体层的结晶性及微观结构,使较多的噻吩环面垂直于衬底、得到π-π堆积方向平行于衬底的二维微晶粒薄片结构,这种微观结构有效地形成了二维共轭电荷传输通道,完善了在RR-P3HT工作层生长过程中的自组织机理;并且对于RR-P3HT半导体工作层来说,慢速生长过程比快速生长过程更有利于有效的二维共轭微晶粒薄片生长,更能完善RR-P3HT工作层生长过程中的自组织机理. 关键词： 高度区域规则的聚(3-己基噻吩)有机场效应晶体管 同步辐射掠入射X射线衍射 自组织机理 微观结构     

Enhanced photovoltaic performance of solution-processed Sb2Se3 thin film solar cells by optimizing device structure

Thin-film solar cells have attracted worldwide attention due to their high efficiency and low cost. Antimony selenide (Sb₂Se₃) is a promising light absorption material candidate for thin-film solar cells due to its suitable band gap, abundance, low toxicity, and high chemical stability. Herein, we fabricate an Sb₂Se₃ thin film solar cell using a simple hydrazine solution process. By controlling the thickness of the photoactive layer and inserting a poly(3-hexylthiophene) hole-transporting layer, an Sb₂Se₃ solar cell with a power conversion efficiency of 2.45% was achieved.     

瞬态光电流对有机薄膜光伏器件中肖特基接触的研究

制备了结构为氧化铟锡(ITO)/有机半导体/金属的有机薄膜光伏器件,电流--电压曲线显示其具有整流特性但有机半导体和电极间肖特基接触的内建电场方向很难判定.为了研究有机半导体和电极的肖特基接触特性,分别制备了结构为ITO/有机绝缘层/有机半导体/金属和ITO/有机半导体/有机绝缘层/金属的器件,通过调制激光照射下器件的瞬态光电流方向可容易判断有机半导体和电极间肖特基接触的内建电场方向,外加偏压下瞬态光电流的强度变化进一步证实了判断的正确性.     

Preparation of poly(3-hexylthiophene)/graphene nanocomposite via in situ reduction of modified graphite oxide sheets

Poly(3-hexylthiophene) (P3HT)/graphene nanocomposites were facilely prepared via an in situ reduction of modified graphite oxide (mGO) in the presence of P3HT. The chemical and aggregated structures of the P3HT/mGO nanocomposites were successfully characterized by means of atomic force microscope (AFM), transmission electron microscope (TEM), photoluminescence (PL), Raman spectra, X-ray photoelectron spectroscopy (XPS) and UV-vis measurements. Coated by P3HT, reduced modified graphite oxide (re-mGO) could significantly improve their processing problem in common organic solvent. It was shown that P3HT chains were attached to re-mGO sheets closely and there existed the pi-pi interaction between P3HT and re-mGO. The P3HT/mGO nanocomposites exhibited good dispersion in chloroform and show high storage stability (>20 days). This finding provides an efficient method for fabricating a light energy conversion materials with new optical and electrical properties, combining excellent mechanics, heat-stabilization properties of graphene and excellent optical, electrical, processing and film forming properties of soluble polythiophene materials.     

Top contact organic field effect transistors fabricated using a photolithographic process

This paper proposes an effective method of fabricating top contact organic field effect transistors by using a pho-tolithographic process.The semiconductor layer is protected by a passivation layer.Through photolithographic and etching processes,parts of the passivation layer are etched off to form source/drain electrode patterns.Combined with conventional evaporation and lift-off techniques,organic field effect transistors with a top contact are fabricated suc-cessfully,whose properties are comparable to those prepared with the shadow mask method and one order of magnitude higher than the bottom contact devices fabricated by using a photolithographic process.     

有机场效应晶体管材料及器件研究进展

有机场效应晶体管(organic field—effect transistor，OFET)作为新一代半导体晶体管因其广阔的应用前景和近年来技术上的突飞猛进，使之成为微电子和信息领域科学研究和产品开发中热门的话题之一．文章慨述了有机场效应晶体管的材料研究、器件制备技术以及有机场效应晶体管在各领域中应用的最新进展．     

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.     

Investigating the performance of P3HT:PCBM organic solar cells involving gamma-irradiated PEDOT:PSS layer

In this work, we investigated for the first time the characteristics of (poly (3-hexylthiopene) and [6, 6]-phenyl C61-butyric acid methyl ester) (P3HT:PCBM) blends-based organic solar cell with 1.25?mg/mL boric-acid (H₃BO₃)-doped poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) layer which is irradiated under the 40 Gray (Gy) dose of gamma (γ) ray. Experimental results showed that the parameters of solar cell improved with exposure to low-dose gamma radiation. In particular, it has provided a significant improvement in short-circuit current density (J_sc) and power conversion efficiency (PCE). About 49% increase in PCE to 1.22% and 40% increase in J_sc to 6.28?mA/cm² was obtained between the bare device and the device containing irradiated PEDOT:PSS:H₃BO₃. Also, it was determined that the H₃BO₃-doped PEDOT:PSS is more stable to temperature. More importantly, solar cell containing gamma-irradiated PEDOT:PSS:H₃BO₃ showed best performance comparing to conventional PEDOT:PSS-based cell.     

非溶剂掺杂完善自组织机理提升高度区域规则的(3-己基噻吩)有机场效应晶体管器件性能的研究

为了保证在低温加工及溶液制备的情况下,能够提升高度区域规则的聚(3-己基噻吩) (RR-P3HT)有机场效应晶体管(OFET)的器件性能,本文研究了室温下乙醇及乙腈非溶剂的掺杂,及其对高分子自组织机理与导致的RR-P3HT OFET电学性能的影响.实验发现,适量进行乙醇及乙腈非溶剂的掺杂,将促进RR-P3HT薄膜形成更多期望的微晶粒薄片结构,完善高分子自组织机理,导致RR-P3HT OFET电学性能的提升.实验表明,在RR-P3HT溶液中进行5 %乙腈添加后,其器件场效应迁移率的值由原来的4.04×10< 关键词： 高度区域规则的聚(3-己基噻吩)有机场效应晶体管 非溶剂掺杂 自组织机理 场效应迁移率     

有机薄膜晶体管中接触效应的研究

研究了接触效应对有机薄膜晶体管性能的影响.首先在n型重掺杂Si片上制备了以M_OO₃修饰的Al电极为源漏电极的Pentacene基OTFTs(organic thin film transistors),器件场效应迁移率μ_ef达到0.42 cm²/V ·s,阈值电压V_T为-9.16 V,开关比4.7×10³.通过中间探针法,对器件电势分布做了定性判断 关键词： 有机薄膜晶体管 场效应迁移率 接触效应 电荷漂移     

Bulk heterojunction organic photovoltaic cell fabricated by the electrospray deposition method using mixed organic solvent

A high‐efficiency bulk heterojunction organic photovoltaic cell (OPV) was achieved by the electrospray deposition method. The surface roughness of the P3HT:PCBM thin film can be reduced using the mixed solvent consisting of o‐dichlorobenzene (o‐DCB) and acetone. The effect of acetone concentration is related to its dielectric constant. Under an optimized concentration of acetone in o‐DCB (20 vol%), the P3HT/PCBM active layer with a smooth surface can be formed, and the power conversion efficiency of the OPV was 1.9%.

     

Tandem organic light-emitting diode with a molybdenum tri-oxide thin film interconnector layer

A 10-nm-thick molybdenum tri-oxide(MoO3) thin film was used as the interconnector layer in tandem organic lightemitting devices(OLEDs).The tandem OLEDs with two identical emissive units consisting of N,N-bis(naphthalen-1-yl)N,N-bis(phenyl)-benzidine(NPB) /tris(8-hydroxyquinoline) aluminum(Alq3) exhibited current efficiency-current density characteristics superior to the conventional single-unit devices.At 20 mA/cm2,the current efficiency of the tandem OLEDs using the interconnector layers of MoO3 thin film was about 4.0 cd/A,which is about twice that of the corresponding conventional single-unit device(1.8cd/A).The tandem OLED showed a higher power efficiency than the conventional single-unit device for luminance over 1200cd/m2.The experimental results demonstrated that a MoO3 thin film with a proper thickness can be used as an effective interconnector layer in tandem OLEDs.Such an interconnector layer can be easily fabricated by simple thermal evaporation,greatly simplifying the device processing and fabrication processes required by previously reported interconnector layers.A possible explanation was proposed for the carrier generation of the MoO3 interconnector layer.     

有机薄膜电致发光材料与器件研究进展

有机电致发光薄膜近年来得到了迅猛的发展,是未来平板式全固体彩色电视机的技术关键。本文介绍了国内外此项技术的发展,以期对今后的工作有所借鉴     

Tandem organic light-emitting diode with molybdenum tri-oxide thin film interconnector layer

A 10-nm thickness molybdenum tri-oxide (MoO₃) thin film was used as the interconnector layer in tandem organic light-emitting devices (OLEDs). The tandem OLEDs with two identical emissive units consisting of N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine (NPB)/tris(8-hydroxyquinoline) aluminum (Alq₃) exhibited current efficiency-current density characteristics superior to the conventional single-unit devices. At 20 mA/cm², the current efficiency of the tandem OLEDs using the interconnector layers of MoO₃ thin film was about 4.0 cd/A, which is about twice of that of the corresponding conventional single-unit device (1.8 cd/A). The tandem OLED showed a higher power efficiency than the conventional single-unit device for luminance over 1200 cd/m². The experimental results demonstrated that a MoO₃ thin film with a proper thickness can be used as an effective interconnector layer in tandem OLEDs. Such an interconnector layer can be easily fabricated by simple thermal evaporation, greatly simplifying the device processing and fabrication processes required by previously reported interconnector layers. A possible explanation was proposed for the carrier generation of the MoO₃ interconnector layer.     

Hole mobility and trapping in PVK films doped with CdSe/CdS and CdSe quantum dots

Experimental study of the hole mobility in polyvinylcarbazole (PVK) films doped with two kinds of nanocrystals, on bare core CdSe and core-shell CdSe/CdS quantum dots, with concentrations ranging from 3 · 10¹⁰ to 3 · 10¹⁵ cm⁻³, is presented. The quantum dots investigated were made using colloidal chemistry. The hole mobility was measured using the time-of-flight technique as a function of the applied electrical field in the range 10⁵–10⁶ V/cm and for temperatures from 20°C to 50°C. The transient curves, being featureless on a linear plot, show on a double logarithmic scale a sharp inflection point indicating a dispersive carrier drift process. The recovered values of the mobility are in the range 3 · 10⁻⁸–10⁻⁶ cm²·V⁻¹·s⁻¹ and their field and temperature dependences can be analyzed formally within the framework of the Gaussian disorder model proposed by B?ssler. The energetic disorder is, within the experimental accuracy, independent of the concentration and type of quantum dots for the CdSe quantum dots at all concentrations and for the CdS/CdSe quantum dots up to 10¹⁴ cm⁻³. The spatial disorder factors are very large (from 5.3 to 8.7) and do not depend in a systematic way upon the type and concentration of quantum dots (QDs). The experiments show that the apparent mobility does not change considerably with concentration, but it was found that the samples with CdSe/CdS quantum dots at concentrations from 10¹⁵ to 3 · 10¹⁵ cm⁻³ show a decreased photocurrent response. The dependence of the time-integrated transients (corresponding to the full charge value) upon the quantum-dot concentration has been determined. Differences in total photogenerated charge for pure and doped polymer films imply that the quantum dots of that type are the hole traps with capture times much more smaller than the transit time and with emission times a few orders longer than the transit time. CdSe quantum dots without a shell do not seem to exhibit the same properties as core shells and do not produce considerable changes in the charge transfer, even at a density of 10¹⁵ cm⁻³.     

Preheated solvent exposure on P3HT:PCBM thin film: A facile strategy to enhance performance in bulk heterojunction photovoltaic cells

In this study, we explored the ability of a preheated solvent (methanol) to induce characteristic changes at the organic active layer/metal interface, thereby improving the performance of fabricated organic photovoltaic (OPV) cells composed of poly(3-hexylthiopene) (P3HT) and a [6,6]-phenyl-C₇₁-butyric acid methyl ester (PCBM) photoactive blend. Our results demonstrate that exposure to methanol (at room temperature, or preheated at 45 °C or 65 °C) improves the performance of the fabricated OPV cells. After preheated methanol exposure, the P3HT:PCBM thin films were tested for crystallinity, morphology, mobility, and photovoltaic characteristics. Our results revealed that use of the preheated solvent on the organic active layer significantly influences the micro/nano scale morphology and phase segregation of the P3HT:PCBM thin films, as well as the charge carrier mobility. It is hypothesized that the side chain ordering of P3HT and redistribution of PCBM could be results of the modified active layer. Consequently, OPV cells modified with the methanol preheated at 65 °C exhibited a power conversion efficiency (PCE) of 3.36%, with open-circuit voltage of 0.59 V, short-circuit current density of 13.83 mA/cm², and fill-factor of 0.41. In contrast, the unmodified P3HT:PCBM thin film (without methanol exposure) showed a PCE of only 2.13%.