Acceptor-rich bulk heterojunction polymer solar cells with balanced charge mobilities

In this work, we reported efficient polymer solar cells with balanced hole/electron mobilities tuned by the acceptor content in bulk heterojunction blend films. The photovoltaic cells were fabricated with two new wide band-gap D-A polymers PBDDIDT and PBDDIDTT as the donor material. The molecular conformations of new polymers are carefully evaluated by theoretical calculations. The results of photovoltaic studies show that two devices reach their optimal conditions with rich PC₇₁BM content up to 80% in blend films, which is uncommon with most of reported PSCs. The as-cast devices based on PBDDIDT and PBDDIDTT reveal good photovoltaic performance with PCE of 7.04% and 6.40%, respectively. The influence of PC₇₁BM content on photovoltaic properties is further detailed studied by photoluminescence emission spectra, charge mobilities and heterojunction morphology. The results exhibit that more efficient charge transport between donor and acceptor occurs in rich PC₇₁BM blend films. Meanwhile, the hole and electron mobilities are simultaneously enhanced and afford a good balance in rich PC₇₁BM blend films (D/A, 1:4) which is critical for the improvement of current density and fill factors.     

Investigation of the role of Nb on Pd−Zr−Zn catalyst in methanol steam reforming for hydrogen production

Methanol steam reforming is regarded as a very promising process to generate H₂ suitable for fuel cells. Typically, the Pd-based catalysts can catalyze efficiently methanol steam reforming for hydrogen production. But their high selectivity to CO, a byproduct of methanol reforming reaction, severely limits their potential application. In this work, a series of Nb-modified Pd−Zr−Zn catalysts with different Nb loadings were prepared to study their catalytic activities with more focus on the role of Nb on Pd−Zr−Zn catalyst for methanol steam reforming. The prepared catalysts were fully analyzed by using various characterization techniques, for example, ICP, BET, SEM, XRD, H₂-TPR, NH₃-TPD, HRTEM, CO chemisorption, XPS, and Raman. The experimental results showed that an increase in Nb loading for the Nb-modified Pd−Zr−Zn catalysts led to a decrease of the methanol conversion and H₂ production rate. This was probably due to the decrease in the amount of oxygen vacancies on the catalyst surface. However, introduction of Nb into Pd−Zr−Zn catalyst increased the acid strength on the catalytic surface. The aldehyde species derived from methanol decomposition were readily transformed to HCOOH, thus yielding high selectivity to CO₂ for the Nb-modified Pd−Zr−Zn catalysts. Significantly, the addition of Nb to Pd−Zr−Zn catalyst facilitated the incorporation of Pd into the ZnO lattices, which led to the formation of Pd−Zn alloy. Consequently, the Nb-modified Pd−Zr−Zn catalysts exhibited significantly lower CO selectivity and production rate than the Pd−Zr−Zn catalyst. From the results, this work offers a new way to the rational design of selective methanol steam reforming catalysts to decrease the formation of byproduct CO.     

A new soluble poly(bithiophene)-co-3,4-di(methoxycarbonyl)methyl thiophene for LED

The regioregular polyalkylthiophene reported in this contribution has been electrochemically synthesised starting from a 3,4-bis-methoxyacetyl-terthiophene and carefully characterised. Photoluminescence analysis gave, both in solution and in films, very appreciable quantum yield values and LED devices realised with Ca cathode provided a value of red electroluminescence comparable with those of regioregular poly(3-alkylthiophene)s in the monolayer active material architecture, while if a blend with poly-N-vinylcarbazole and 2-(4-t-butyl-phenyl)-5-(4-biphenyl)-1,3,4-oxadiazole constitutes the active layer a white emission is observed.     

阴离子树枝状聚酰胺-胺在有机微粒助留助滤体系中的应用

通过碱性水解将端酯基的半代树枝状聚酰胺-胺(Gn.5PAMAM)改性为外层基团为羧酸钠的阴离子树枝状聚酰胺-胺(A-Gn.5PAMAM),并通过红外光谱进行了结构表征。将A-Gn.5PAMAM作为有机阴离子微粒组分与星形阳离子聚丙烯酰胺(S-CPAM)及阳离子聚丙烯酰胺(CPAM)组成有机微粒助留助滤体系,系统地研究了该有机微粒体系对漂白旧报纸脱墨浆的助留助滤效果。结果表明,S-CPAM(CPAM)-(A-Gn.5PAMAM)有机微粒体系对纸料具有较好的助留助滤作用效果;高代数的A-Gn.5PAMAM对纸料小絮块的絮聚能力优于低代数产物;该有机微粒助留助留体系可以适应较宽的pH值范围,且抵抗高剪切作用的能力较强。研究同时表明,A-Gn.5PAMAM有机阴离子微粒与膨润土无机阴离子微粒具有很好的协同作用。     

Performance of the ZrO2 promoted CuZnO catalyst supported on acetic acid-treated MCM-41 in methanol steam reforming

ZrO₂-promoted CuZnO catalysts were prepared through the sol-gel, conventional impregnation and modified impregnation methods using MCM-41 as support material and applied to the methanol steam reforming (MSR) reaction. The synthesized catalysts were characterized by the XRD, BET, FESEM, TEM, XRF, FTIR, H₂-TPR and TGA methods. The determined physiochemical properties suggested that pretreatment of MCM-41 with acetic acid before metal impregnation remarkably decreases the size of the metal particles and improves their dispersion and reduction behavior. Among the synthesized catalysts, the CuZnOZrO₂/MCM-41 sample prepared through the modified impregnation method exhibited the best catalytic performance with 97.8% methanol conversion, 99.0% H₂ selectivity, 0.4% CO selectivity and the lowest level of coke deposition, at 300 °C. In addition, all catalysts resisted against deactivation by conserving their catalytic activity over 40 h operation, indicating that the use of high surface area MCM-41 as support, the ZrO₂ promoter, and the proper synthesis methods significantly enhanced the catalytic activity in the MSR process.     

Production of hydrogen from steam reforming of methanol carried out by self-combusted CuCr1-xFexO2 (x = 0–1) nanopowders catalyst

In this present work, the delafossite type CuCr_1-xFe_xO₂ (x = 0–1) nanopowder was prepared by a self-combusted glycine nitrate process used for the steam reforming of methanol (SRM). The effectiveness of hydrogen production was upgraded by the preparation of CuCr_1-xFe_xO₂ (x = 0–1). The prepared Cu based materials were characterized by field emission scanning electron microscope studies, X-ray diffraction studies, energy dispersive X-ray studies, and Brunauer-Emmett-Teller studies. The CuCr_1-xFe_xO₂ (x = 0–1) nanopowders were studies by the hydrogen production by methanol steam reforming reaction. The Cu based catalyst exhibited high catalytic activity and hydrogen production rate as 1740 ml/min g-cat at 360 °C. Furthermore, the catalyst nanopowder was stable up to 1200 min without any considerable changes in steam reforming methanol and product selectivity in the SRM process. The production rate of CuCr_1-xFe_xO₂ was improved by the adequate amount of iron incorporation (60%) and adjusted the feeding rate of methanol. These conditions obtain the best performance could reach the hydrogen production of 301.45 (μmol (min g-cat)⁻¹) at 350° over CuCr_0.4Fe_0.6O₂ with a flow rate of 60 sccm.     

Benzothiadiazole[1,2-b:4,3-b′]dithiophene,a new ladder-type multifused block: Synthesis and photovoltaic application

A new fused building block benzothiadiazole[1,2-b:4,3-b′] dithiophene (BTDT) was prepared by covalently locking thiophene unit on both sides of benzothiadiazole (BT). On the basis of this building block, a series of conjugated copolymers containing homopolymer (P1) or electron-rich comonomers such as carbazole (P2), benzodithiophene (P3 and P4) and thiophene (P5) were obtained. All polymers have good solubility in common organic solvents. The thermal, optical, electrochemical and photovoltaic properties of the polymers were investigated systematically. The thiophene units, which were covalently fastened to the BT moiety, enlarged the planarization of the polymer backbone and thus induced stronger intermolecular π–π interaction, meanwhile, decreased the electron-withdrawing ability of the BT unit. The device based on P3:PC₇₁BM exhibited a high open-circuit voltage (V_OC) of 0.96 V and moderate power conversion efficiency (PCE) of 2.16%.     

Nanocubic bimetallic organic framework self-templated from Ni precursor as efficient electrocatalysts for oxygen evolution reaction

Developing highly active and robust oxygen evolution reaction electrocatalysts is indispensable to relieve energy crisis. Herein, firstly, the Ni nanocubes precursor as a self-sustaining template is synthesized through a reflow method. Afterward, the nanocubic NiFe bimetallic organic frameworks was formed under the self-assembly approach between the exogenous Fe²⁺ and released Ni²⁺ from Ni nanocubes with terephthalic acid organic ligand on the Ni nanocubes precursor, i.e Ni nanocubes@MIL-53(NiFe). The synthesized Ni nanocubes@MIL-53(NiFe) exhibit excellent activity, which only requires the overpotential of 271 and 388 mV to deliver the current density of 20 and 100 mA cm⁻² in alkaline solution (1.0 M KOH). The noticeable catalytic performance can be ascribed to the aspects as following: 1) Ni nanocubes as a template provides a Ni source during the self-assembled process; 2) the metal-metal coupling effect arisen within the Ni and Fe atom is substantially contributed to the oxygen evolution reaction performance; 3) the abundant active sites, enhanced electron transport ability also endow the superior electrocatalytic oxygen evolution reaction activity; 4) rich carboxyl groups in the metal-organic frameworks structure could enhance the hydrophilicity of the catalysts. We anticipate that our study would extend the design and exploration of active metal-organic frameworks on energy conversion field.     

3,7-Bis((E)-2-oxoindolin-3-ylidene)-3,7-dihydrobenzo[1,2-b:4,5-b′]dithiophene-2,6-dione (IBDT) based polymer with balanced ambipolar charge transport performance

A novel acceptor building block, 3,7-bis((E)-2-oxoindolin-3-ylidene)-3,7-dihydrobenzo[1,2-b:4,5-b′]dithiophene-2,6-dione (IBDT), is developed to construct a donor-acceptor polymer PIBDTBT-40. This polymer has favorable highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels for balanced ambipolar charge transport. Organic thin film transistors (OTFTs) based on this polymer shows well-balanced ambipolar characteristics with electron mobility of 0.14 cm² V⁻¹ s⁻¹ and hole mobility of 0.10 cm² V⁻¹ s⁻¹ in bottom-gate bottom-contact devices. This polymer is a promising semiconductor for solution processable organic electronics such as CMOS-like logic circuits.     

Bithiazole-based copolymer with deep HOMO level and noncovalent conformational lock for organic photovoltaics

To match with the state-the-art-of non-fullerene acceptor for polymer solar cells (PSCs), it is urgent to develop high performance wide-bandgap (WBG) copolymer donors with deep highest occupied molecular orbital (HOMO) level and highly planar backbone to further promote the device efficiency. A new WBG copolymer PBDTBTz, poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithi ophene))-alt-(5,5’-(-4,4’-dinonyl-2,2’-bithiazole))], which is based on benzodithiophene (BDT) as donor unit and 4,4’-dinonyl-2,2’-bithiazole (BTz) as acceptor unit is prepared for non-fullerene PSCs. Due to the strong electron-withdrawing effect, BTz unit can dramatically lower the HOMO level of PBDTBTz to −5.60 eV. Notably, double noncovalent conformational locks (N⋯S) of BTz are formed in the backbone to reduce the steric hindrance and favor a highly planar geometry for efficient charge transport and molecular packing. As a result, the device based on PBDTBTz as donor and 3,9-bis(2-methylene-((3-(1,1-dic-yanomethylene)-6,7-difluoro)-indanone))-5,5,11, 11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d']-s-indaceno[1,2-b:5,6-b']dithiophen e(IT-4F) as acceptor afforded a high open circuit voltage (V_oc) of 0.92 V, which is the highest value for IT-4F-based PSCs reported so far. Furthermore, the device operated well with a negligible driving force (ΔE_HOMO) of as small as 0.06 eV. These results revealed that combination of electron-withdrawing bithiazole and double noncovalent conformational lock of N⋯S is a promising molecular design concept of polymer donor with deep and planar structure for high performance PSCs.