Indacenodithienothiophene based chromophore with cyclopentadienylidenehydrazine acceptor moieties

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3,6‐Dialkylthieno[3,2‐b]thiophene moiety as a soluble and electron donating unit preserving the coplanarity of photovoltaic low band gap copolymers

It has been shown recently, that the presence of alkyl side chains at the 3‐positions on the thiophene rings placed next to 2,1,3‐benzothiadiazole core in the backbone of several conjugated polymers results in severe steric hindrance and prevents efficient planarity of the thiophene‐2,1,3‐benzothiadiazole‐thiophene (TBzT) segment. Both properties have a strong influence on the optoelectronic properties of the polymer and need to be considered when the polymer is to be used for organic electronics applications. In this work, we modified a previously synthesized oligothiophene copolymer, consisting of two 3,4′‐dialkyl‐2,2′‐bithiophene units attached to a 2,1,3‐benzothiadiazole unit (TBzT segment) and a thieno[3,2‐b]thiophene unit, by optimizing the lateral alkyl side chains following a density functional theory investigation. It is demonstrated that eliminating the alkyl side chains from the 3‐positions of the TBzT segment and anchoring them onto the thieno[3,2‐b]thiophene, using an efficient synthesis of the 3,6‐dihexylthieno[3,2‐b]thiophene unit, allows us to reduce the energy band gap. In addition, the chemical modification leads to a better charge transport and to an enhanced photovoltaic efficiency of polymer/fullerene blends. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Porphyrin–diindenothieno[2,3‐b]thiophene alternating copolymer—a blue‐light harvester in ternary‐blend polymer solar cells

Porphyrin, despite chosen by Nature as light harvesting units, hasn't revealed its full potentials as a structural unit in porphyrin‐incorporated polymers (PPors). A novel PPor was synthesized to investigate the origins of the low performances of PPor‐based polymer solar cells (PSCs). The polymer features broad absorption in the blue‐light region, because the diindenothieno[2,3‐b]thiophene (DITT) unit extended the conjugation in the polymer backbone. PPor‐DITT/PC₇₁BM based PSCs have a high V_oc (0.79 V). Their low J_sc and fill factor (FF) were attributed to the un‐optimized morphology, as indicated by the photoluminescence quenching and atomic force microscopy (AFM) experiments. Using PPor‐DITT as a blue‐light harvesting dopant in an amorphous host leverage the strong 400–550 nm absorption of PPor‐DITT and circumvent the difficulties in reaching optimized morphology in the PPor/PCBM thin films. An addition of 2 wt % of PPor‐DITT in ternary‐blend PSCs resulted in a 10 % increase of external quantum efficiency (EQE) in the blue‐light region. However, in a crystalline host, the dopant decreased the crystallinity of the host and led to large drops in FF and power conversion efficiencies (PCEs). The study provides an alternative route and expands the application of PPors in PSCs as a blue‐light harvester in ternary‐blend PSCs using amorphous polymers as host. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

一锅法制备S型异质结光催化剂Fe2O3/Fe2TiO5及其高效降解有机污染物性能

首次采用简单的一锅法制备了Fe₂O₃/Fe₂TiO₅异质结纳米材料。构建S型异质结后,与纯的Fe₂O₃和Fe₂TiO₅相比,Fe₂O₃/Fe₂TiO₅复合材料表现出更高的光催化降解速率和效率。经过2.5 h的光照后,Fe₂O₃/Fe₂TiO₅可以降解接近100%的亚甲基蓝（MB）。在Fe₂O₃/Fe₂TiO₅复合材料中,Fe₂O₃和Fe₂TiO₅之间形成了内建电场,可以促进光生电子-空穴对的分离。因此,具有更高能量的Fe₂TiO₅导带中的电子和具有更高能量的Fe₂O₃价带中的空穴可以得到有效的保留,从而使它们更加有效地扩散到催化剂表面,并参加降解反应。此外,Fe₂O₃/Fe₂TiO₅复合材料具有很好的光催化稳定性。     

三维花状Bi2WO6/BiOBr异质结的制备及对多种染料的降解性能

利用水热法以十二烷基二甲基溴化铵(DDAB)和十六烷基三甲基溴化铵(CTAB)为结构导向剂以及溴源,成功地制备了三维花状Bi₂WO₆/BiOBr异质结。通过X射线粉末衍射、扫描电镜、透射电镜、紫外可见漫反射光谱、光电流、Nyquist曲线和电子顺磁共振分别对样品的结构、形貌、组成和光电化学性能进行了表征。结果表明,20~30 nm的BiOBr纳米粒子均匀地附着在Bi₂WO₆薄片上形成三维花状结构。Bi₂WO₆/BiOBr与纯Bi₂WO₆相比,扩展了可见光的响应范围,且提高了催化剂光生电子与空穴的分离效率。光降解实验表明w_DDAB/w_CTAB=2.6时Bi₂WO₆/BiOBr的光催化性能最优。在300 W氙灯(波长>420 nm)可见光照射下,其在降解罗丹明B中表现出最高的反应速率常数(0.0997 min^-1),分别约为Bi₂WO₆(0.0376 min^-1)和BT?4(0.0523 min^-1,w_DDAB/w_CTAB=3.9)的2.7倍和1.9倍,且6个循环后活性依然没有明显衰减。Bi₂WO₆/BiOBr异质结还可以无选择性地降解其他类型的有机染料,如亚甲基蓝、孔雀石绿和甲基橙。最后,基于活性物种捕获实验和Mulliken原子电负性理论计算结果,提出了Bi₂WO₆/BiOBr异质结的光降解机理。     

同型异质表面修饰提高La2NiO4+δ阴极的电催化活性

构建异质结界面来改性传统的阴极材料已广泛应用于提高固体氧化物燃料电池(SOFC)阴极氧还原反应(ORR)活性的研究。 本文研究发现,在传统的La₂NiO_4+δ(LNO)阴极表面,表面修饰同型的Pr₂NiO_4+δ(PNO) 薄膜能够有效地加速其ORR动力学。 同时,也揭示了表面修饰提高ORR活性的机理。 首先,调控工艺条件,LNO薄膜出现了高催化活性的(110)晶面。 其次,厚度约为5 nm的PNO外延层沉积在LNO表面显示出最小的极化电阻,其极化电阻比相同厚度LNO参照的小近21倍。 由于异质结表面氧缺陷化学的不同,PNO(~5 nm)表面修饰的异质结表现出优越的ORR活性。 其中,多孔的LNO本体提供了一条有利于传输氧离子和电子的途径,而PNO修饰提供了丰富的表面氧缺陷,从而进一步增强了阴极的ORR活性。     

SiC/Pt/CdS纳米棒Z型异质结的制备及其高效光催化产氢性能

In this study, a novel silicon carbide/platinum/cadmium sulfide (SiC/Pt/CdS) Z-scheme heterojunction nanorod is constructed using a simple chemical reduction-assisted hydrothermal method, in which Pt nanoparticles are anchored at the interface of SiC nanorods and CdS nanoparticles to induce an electron-hole pair transfer along the Z-scheme transport path. Multiple characterization techniques are used to analyze the structure, morphology, and properties of these materials. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results show that the SiC/Pt/CdS materials with good crystal structure are successfully synthesized. Transmission electron microscopy reveals that Pt nanoparticles grow between the interfaces of SiC nanorods and CdS nanoparticles. UV-Vis diffuse reflectance spectroscopy shows that the as-prepared Z-scheme heterojunction samples have a wider light absorption range in comparison with pristine CdS materials. Photoluminescence spectroscopy and the transient photocurrent response further demonstrate that the SiC/Pt/CdS nanorod sample with an optimal molar ratio possesses the highest electron-hole pair separation efficiency. The loading amount of CdS on the surface of SiC/Pt nanorods is effectively adjusted by controlling the molar ratio of SiC and CdS to achieve the optimal performance of the SiC/Pt/CdS nanorod photocatalysts. The optimal H₂ evolution capacity is achieved at SiC : CdS = 5 : 1 (molar ratio) and the maximum H₂ evolution rate reaches a high value of 122.3 µmol·h⁻¹. In addition, scanning electron microscopy, XRD, and XPS analyses show that the morphology and crystal structure of the SiC/Pt/CdS photocatalyst remain unchanged after three cycles of activity testing, indicating that the SiC/Pt/CdS nanocomposite has a stable structure for H₂ evolution under visible light. To prove the Z-scheme transfer mechanism of electron-hole pairs, selective photo-deposition technology is used to simultaneously carry out the photo-reduction deposition of Au nanoparticles and photo-oxidation deposition of Mn₃O₄ nanoparticles in the photoreaction. The experimental results indicate that during photocatalysis, the electrons in the conduction band of CdS participate mainly in the reduction reaction, and the holes in the valence band of SiC are more likely to undergo the oxidation reaction. The electrons in the conduction band of SiC combine with the holes in the valence band of CdS to form a Z-scheme transport path. Therefore, a possible Z-scheme charge migration path in SiC/Pt/CdS nanorods during photocatalytic H₂ production is proposed to explain the enhancement in the activity. This study provides a new strategy for synthesizing a Z-scheme photocatalytic system based on SiC nanorods. Based on the characterization results, it is determined that SiC/Pt/CdS nanocomposites are highly efficient, inexpensive, easy to prepare, and are stable structures for H₂ evolution under visible light with outstanding commercial application prospects.     

Introducing sulfur vacancies and in-plane SnS2/SnO2 heterojunction in SnS2 nanosheets to promote photocatalytic activity

Due to the relatively sluggish charge carrier separation in metal sulfides, the photocatalytic activity of them is still far lower than expected. Herein, sulfur vacancies and in-plane SnS₂/SnO₂ heterojunction were successfully introduced into the SnS₂ nanosheets through high energy ball-milling. These defective structures were studied by the electron paramagnetic resonance, Raman spectra, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscope analyses. The sulfur vacancies and in-plane heterojunctions strongly accelerate the separation of photoexcited electron-hole pairs, as confirmed by the photoluminescence emission spectra and time-resolved photoluminescence decay spectra. The introduction of sulfur vacancies and in-plane heterojunction in SnS₂ nanosheets results in roughly six times higher photodegrading rate for methyl orange and four times higher photocatalytic reduction rate of Cr⁶⁺ than those of pure SnS₂ nanosheets.     

Interface configuration effects on excitation,exciton dissociation,and charge recombination in organic photovoltaic heterojunction

The morphology of donor-acceptor heterojunction interface significantly affects the electron/hole processes in organic solar cells, including charge transfer (CT), exciton dissociation (ED), and charge recombination (CR). Here, to investigate interface molecular configuration effects, the donor-acceptor complexes with face-on, edge-on, and end-on configurations were constructed as model systems for the p-SIDT(FBTTh₂)₂/C₆₀ heterojunction. The geometries, electronic structures, and excitation properties of monomers and the complexes with three configurations were studied based on density functional theory (DFT) and time-dependent DFT calculations with optimally tuned range separation parameters and solid polarization effects. In terms of Marcus theory, the rate constants of ED and CR processes were analyzed. The results show that most of the excited states for p-SIDT(FBTTh₂)₂ exhibit an intramolecular CT character, and the similarity of the excitation characters (CT and local excitation) and energies among three complexes with different configurations indicate that the electronic structure and excitation properties are insensitive to the interfacial molecular configurations. However, the rates of ED and CR processes heavily depend on it. These results underline the importance of controlling molecular configuration and then the morphology at the heterojunction interface in organic solar cells.