Co-reporter:Feiyan Dong 董飞燕;Yanjun Guo 郭延军;Peng Xu 徐鹏;Xiong Yin 殷雄
Science China Materials 2017 Volume 60( Issue 4) pp:295-303
Publication Date(Web):2017 April
DOI:10.1007/s40843-017-9009-8
MoS2/Co3S4 composite films were prepared via a facile one-step hydrothermal method, and used as efficient and low-cost Pt-free counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). Characterizations revealed that Co3S4 and MoS2 were obtained simultaneously during the facile hydrothermal process. The composites afforded a promising synergistic effect on the catalyzing of triiodide reduction. Enhanced electrocatalytic performance of the resultant composite films was confirmed through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analyses. DSSCs using MoS2/Co3S4 composite CEs outperform the devices with pristine MoS2 or Co3S4 CEs in power conversion efficiency (PCE). Furthermore, a PCE of 6.77% is obtained for the optimized devices using MoS2/Co3S4 composite CEs measured under standard 1 sun illumination (100 mW cm−2, AM 1.5G), which is comparable to that of the devices fabricated under the same conditions with conventional thermally deposited Pt CEs (7.14%). The results demonstrate that MoS2/Co3S4 composites are promising alternatives to Pt to be applied as CEs for DSSCs.染料敏化太阳电池因其成本低、稳定性好、工艺简便而备受关注. 发展高性能、廉价的材料代替传统的贵金属铂对电极是当前染 料敏化太阳电池领域的研究热点之一. 二硫化钼纳米材料具有高比表面积和大量的催化位点, 是较为理想的铂对电极替代材料之一, 但较 低的电导率限制了二硫化钼对电极性能的进一步提高. 本文首次报道了由二硫化钼纳米材料与金属性的四硫化三钴复合制备染料敏化 太阳电池对电极, 该复合对电极可以利用水热方法一步合成. 研究结果表明, 使用该复合对电极的染料敏化太阳电池光电转换效率可达 6.77%, 接近于使用铂对电极的器件(7.14%), 优于使用单一二硫化钼(4.64%)或四硫化三钴(5.11%)作为对电极的器件.
Co-reporter:Xiong Yin, Zhongzhong Xu, Yanjun Guo, Peng Xu, and Meng He
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 43) pp:29580
Publication Date(Web):October 14, 2016
DOI:10.1021/acsami.6b09326
Perovskite solar cells, which utilize organometal–halide perovskites as light-harvesting materials, have attracted great attention due to their high power conversion efficiency (PCE) and potentially low cost in fabrication. A compact layer of TiO2 or ZnO is generally applied as electron-transport layer (ETL) in a typical perovskite solar cell. In this study, we explored ternary oxides in the TiO2–ZnO system to find new materials for the ETL. Compact layers of titanium zinc oxides were readily prepared on the conducting substrate via spray pyrolysis method. The optical band gap, valence band maximum and conduction band minimum of the ternary oxides varied significantly with the ratio of Ti to Zn, surprisingly, in a nonmonotonic way. When a zinc-rich ternary oxide was applied as ETL for the device, a PCE of 15.10% was achieved, comparable to that of the device using conventional TiO2 ETL. Interestingly, the perovskite layer deposited on the zinc-rich ternary oxide is stable, in sharp contrast with that fabricated on a ZnO layer, which will turn into PbI2 readily when heated. These results indicate that potentially new materials with better performance can be found for ETL of perovskite solar cells in ternary oxides, which deserve more exploration.Keywords: electron-transport layer; hole-blocking layer; perovskite solar cell; ternary oxide; zinc titanate
Co-reporter:Ningning Zhang, Yanjun Guo, Xiong Yin, Meng He, Xiaoping Zou
Materials Letters 2016 Volume 182() pp:248-252
Publication Date(Web):1 November 2016
DOI:10.1016/j.matlet.2016.07.004
•A conceptually new carbon counter electrode for perovskite solar cell was demonstrated.•Device with efficiency of 4.24% was achieved with an optimized carbon electrode.•The work enables new possibilities in choosing material and process to fabricate device.A conceptually new carbon counter electrode for perovskite solar cell was demonstrated, which was fabricated on a separated substrate and then assembled with other components to complete a whole device, in contrast to conventional metal or carbon electrodes which are directly deposited on other component layers of the device. Power conversion efficiency (PCE) of 4.24% was achieved for perovskite solar cell with an optimized carbon electrode. The separation of preparation of electrode and device assembly provides much freedom for the choices of materials and preparation process to fabricate the device.
Co-reporter:Shuai Jiang, Xiong Yin, Juntao Zhang, Xiaoyang Zhu, Jianye Li and Meng He
Nanoscale 2015 vol. 7(Issue 23) pp:10459-10464
Publication Date(Web):11 May 2015
DOI:10.1039/C5NR00788G
Vertical MoS2 nanosheets with both large specific surface areas and sharp, active edges are strongly desirable due to their potential applications as catalysts, sensors and field emitters. Nevertheless, the growth of vertical MoS2 nanosheets is still a challenge and has rarely been reported. In this contribution, vertical ultrathin MoS2 nanosheets were grown on diverse substrates via a facile chemical vapor deposition method using CS2 as the sulfur precursor. To the best of our knowledge, it is the first time that CS2 has been applied as the sulfur source for the CVD growth of MoS2. In comparison with sulfur powder, the conventional sulfur source, CS2, can be imported in the growth chamber by a carrying gas, which provides considerable convenience for controlling growth parameters. Vertical MoS2 nanosheets presented a comparable catalytic activity to Pt on triiodide reduction and were used as efficient counter electrodes in dye-sensitized solar cells.
Co-reporter:Yanfang Wang, Dongliang Chen, Xiong Yin, Peng Xu, Fan Wu, and Meng He
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 47) pp:26226
Publication Date(Web):November 17, 2015
DOI:10.1021/acsami.5b08410
Electromagnetic wave absorbing materials that can exhibit effective absorption in a broad bandwidth at a thin thickness are strongly desired due to their widespread applications in electronic devices. In this study, hybrids of MoS2 and reduced graphene oxide (RGO) were prepared and their microwave absorption performance was investigated for the first time. It was found that a thin sample consisting of 10 wt % MoS2/RGO hybrid in the wax matrix exhibited an effective microwave absorption bandwidth of 5.72 GHz at the thickness less than 2.0 mm. The highest reflection loss of −50.9 dB was observed at 11.68 GHz for a sample with a thickness of 2.3 mm. Results obtained in this study indicate that hybrids of MoS2 and RGO are promising microwave absorbing materials, which can exhibit broad effective absorption bandwidth at low filler loading and thin thickness.Keywords: composite; electromagnetic properties; microwave absorber; MoS2; reduced graphene oxide;
Co-reporter:Xiong Yin;Yanjun Guo;Zhaosheng Xue;Peng Xu;Bin Liu
Nano Research 2015 Volume 8( Issue 6) pp:1997-2003
Publication Date(Web):2015 June
DOI:10.1007/s12274-015-0711-4
Perovskite solar cells are one of the most promising alternatives to conventional photovoltaic devices, and extensive studies are focused on device optimization to further improve their performance. A compact layer of TiO2 is generally used in perovskite solar cells to block holes from reaching the fluorine-doped tin oxide electrode. In this contribution, we engineered a TiO2 compact layer using Nb doping, which resulted in solar cells with a power conversion efficiency (PCE) of 10.26%, which was higher than that of devices with the same configuration but containing a pristine TiO2 compact layer (PCE = 9.22%). The device performance enhancement was attributed to the decreased selective contact resistance and increased charge recombination resistance resulting from Nb doping, which was revealed by the impedance spectroscopy measurements. The developed strategy highlights the importance of interface optimization for perovskite solar cells.
Co-reporter:Hui Li, ;Ze Zhang
Acta Crystallographica Section A 2015 Volume 71( Issue 5) pp:526-533
Publication Date(Web):
DOI:10.1107/S2053273315012103
The core theme of X-ray crystallography is reconstructing the electron-density distribution of crystals under the constraints of observed diffraction data. Nevertheless, reconstruction of the electron-density distribution by straightforward Fourier synthesis is usually hindered due to the well known phase problem and the finite resolution of diffraction data. In analogy with optical imaging systems, the reconstructed electron-density map may be regarded as the image of the real electron-density distribution in crystals. Inspired by image definition evaluation functions applied in the auto-focusing process, two evaluation functions are proposed for the reconstructed electron-density images. One of them is based on the atomicity of the electron-density distribution and properties of Fourier synthesis. Tests were performed on synthetic data of known structures, and it was found that this evaluation function can distinguish the correctly reconstructed electron-density image from wrong ones when diffraction data of atomic resolution are available. An algorithm was established based on this evaluation function and applied in reconstructing the electron-density image from the synthetic data of known structures. The other evaluation function, which is based on the positivity of electron density and constrained power spectrum entropy maximization, was designed for cases where only diffraction data of rather limited resolution are available. Tests on the synthetic data indicate that this evaluation function may identify the correct phase set even for a data set with resolution as low as 3.5 Å. Though no algorithm for structure solution has been figured out based on the latter function, the results presented here provide a new perspective on the phase problem.
Co-reporter:Wantao Liu, Yanyan Fang, Peng Xu, Yuan Lin, Xiong Yin, Guangshi Tang, and Meng He
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 18) pp:16249
Publication Date(Web):August 27, 2014
DOI:10.1021/am5044483
Polypyrrole/reduced graphene oxide (PPy/RGO) composites on the rigid and plastic conducting substrates were fabricated via a facile two-step electrochemical process at low temperature. The polypyrrole/graphene oxide (PPy/GO) composites were first prepared on the substrate with electrochemical polymerization method, and the PPy/RGO composites were subsequently obtained by electrochemically reducing the PPy/GO. The resultant PPy/GO and PPy/RGO composites were porous, in contrast to the dense and flat pristine PPy films. The cyclic voltammetry measurement revealed that resultant composites exhibited a superior catalytic performance for triiodide reduction in the order of PPy/RGO > PPy/GO > PPy. The catalytic activity of PPy/RGO was comparable to that of Pt counter electrode (CE). Under the optimal conditions, an energy conversion efficiency of 6.45% was obtained for a rigid PPy/RGO-based dye-sensitized solar cell, which is 90% of that for a thermally deposited Pt-based device (7.14%). A plastic counter electrode was fabricated by depositing PPy/RGO composites on the plastic ITO/PEN substrate, and then an all-plastic device was assembled and exhibited an energy conversion efficiency of 4.25%, comparable to that of the counterpart using a sputtered-Pt CE (4.83%) on a plastic substrate. These results demonstrated that electrochemical synthesis is a facile low-temperature method to fabricate high-performance RGO/polymer composite-based CEs for plastic DSCs.Keywords: composites; dye-sensitized solar cells; electrochemical polymerization; low-temperature fabrication; plastic substrate; polypyrrole; Pt-free; reduced graphene oxide
Co-reporter:Xiong Yin, Fan Wu, Nianqing Fu, Jing Han, Dongliang Chen, Peng Xu, Meng He, and Yuan Lin
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 17) pp:8423
Publication Date(Web):August 8, 2013
DOI:10.1021/am401719e
A high-performance Pt-free counter electrode (CE) based on poly(3,4-ethylenedioxythiophene) (PEDOT) film for plastic dye-sensitized solar cells (DSCs) has been developed via a facile solid-state polymerization (SSP) approach. The polymerization was simply initiated by sintering the monomer, 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT), at the temperature of 80 °C, which can be applied on the plastic substrate. The cyclic voltammetry measurements revealed that the catalytic activity of the SSP-PEDOT CE for triiodide reduction is comparable with that of the Pt CE. Under optimized conditions, the power conversion efficiency of a DSC with a N719-sensitized TiO2 photoanode and the SSP-PEDOT CE is 7.04% measured under standard 1 sun illumination (100 mW cm–2, AM 1.5), which is very close to that of the device fabricated under the same conditions with a conventional thermally deposited Pt CE (7.35%). Furthermore, taking advantage of the compatibility of the SSP-PEDOT with the plastic substrates, a full plastic N719-sensitized TiO2 solar cell was demonstrated, and an efficiency of 4.65% was achieved, which is comparable with the performance of a plastic DSC with a sputter-deposited Pt CE (5.38%). These results demonstrated that solid-state polymerization initiated at low temperature is a facile and low-cost method of fabricating the high-performance Pt-free CEs for plastic DSCs.Keywords: 2,5-dibromo-3,4-ethylenedioxythiophene; electrochemical impedance spectra; flexible dye-sensitized solar cells; plastic substrate; poly(3,4-ethylenedioxythiophene); solid-state polymerization;
Co-reporter:Xiong Yin, Hailong Zhang, Peng Xu, Jing Han, Jianye Li and Meng He
RSC Advances 2013 vol. 3(Issue 40) pp:18474-18481
Publication Date(Web):29 Aug 2013
DOI:10.1039/C3RA43403F
The nitrogen-doped P90 TiO2 (N-P90), nitrogen-doped reduced graphene oxide (N-RGO) and their composite were synthesized via a one-step annealing treatment process under NH3 atmosphere using commercial P90 TiO2 and GO as starting materials. The as-prepared N-P90, N-RGO and N-P90/N-RGO composite were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible diffuse reflectance spectroscopy (DRS). The results indicated that both the reduction of graphene oxide and the incorporation of nitrogen into both RGO and TiO2 matrices were accomplished simultaneously in the facile process. The photocatalytic activity of the as-prepared samples was evaluated using the degradation of methylene blue (MB) under visible light irradiation. N-P90/N-RGO composites showed a significantly enhanced photocatalytic performance compared with P90 TiO2, N-P90 and N-P90/RGO composites. The higher photocatalytic activity of N-P90/N-RGO composites can be ascribed to the more efficient separation of the photogenerated charges resulting from the improved electrical conductivity of the N-RGO sheets, as well as the enhanced absorption in the visible light region. Overall, this work demonstrated a facile approach of incorporating nitrogen into commercial TiO2 and RGO simultaneously and a novel strategy of fabricating a visible light-active photocatalyst with improved efficiency for mass application.
Co-reporter:Meng He, Hiroki Okudera, Arndt Simon, J. Köhler, Shifeng Jin, Xiaolong Chen
Journal of Solid State Chemistry 2013 Volume 197() pp:466-470
Publication Date(Web):January 2013
DOI:10.1016/j.jssc.2012.08.034
Crystal structures of both polymorphs of Li4B2O5 were determined. The high temperature phase crystallized in a monoclinic space group I2/a with lattice constants a=10.2269(18) Å, b=4.6988(5) Å, c=8.7862(16) Å, and β=93.562(14)°, while the low temperature one crystallized in an orthorhombic space group Pca21 with lattice constants a=10.1497(8) Å, b=4.7365(5) Å, c=17.5880(14) Å. Though the lattice of the low temperature phase is of higher symmetry than that of the high temperature one, the structure itself loses symmetry elements when it transforms from the high temperature phase to the low temperature polymorph. The bond strain associated with the high temperature structure is supposed to be the reason for the phase transition. A slight increase in volume per formula unit was observed when Li4B2O5 transforms from the high temperature polymorph to low temperature structure, which is quite unusual and has to be studied further.Graphical abstractThe monoclinic high temperature polymorph of Li4B2O5 loses symmetry elements when it transforms into the orthorhombic low temperature phase to relieve the bond strain.Highlights► Structures of two polymorphs of Li4B2O5 are determined. ► The high and low temperature phases are monoclinic and orthorhombic, respectively. ► A slight larger molar volume was observed for the low temperature phase. ► Symmetry elements are lost in the phase transition from high to low temperature.
Co-reporter:Aming Xie, Mengxiao Sun, Kun Zhang, Wanchun Jiang, Fan Wu and Meng He
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 36) pp:NaN24936-24936
Publication Date(Web):2016/08/08
DOI:10.1039/C6CP04600B
Electromagnetic pollution is rising all over the world. Compared with electromagnetic waves reflection, electromagnetic absorption (EA) is a better choice to balance electromagnetic applications and human health. The highly conductive networks in composites, as well as in species, and the intensity of defect polarization are the most important factors to improving the EA performance of a dielectric material. In this study, an in situ one-pot hydrothermal growth of MoS2 layers on reduced graphene oxide (RGO) surfaces was developed for the synthesis of RGO/MoS2 nanosheets. With a filler loading ratio of 20 wt%, the composite of the RGO/MoS2 nanosheets could build conductive networks and exhibited an effective EA bandwidth (lower than −10 dB) of 5.7 GHz and a minimum reflection loss (RL) of −60 dB. The results revealed that the as-prepared RGO/MoS2 nanosheets are promising EA materials, with broad and strong absorption properties at a low filler loading and low thickness.
