The synthesis of MDMO-PPV capped PbS nanorods and their application in solar cells

Poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) capped PbS nanorods about 100 nm in diameter and 400 nm in length were synthesized via a hydrothermal route in toluene and dimethylsulfoxide solution. By blending the PbS nanorods with the MDMO-PPV as the active layer, bulk heterojunction solar cells with an indium tin oxide (ITO)/polyethylenedioxythiophene/polystyrenesulphonate (PEDOT: PSS)/MDMO-PPV: PbS nanorods/Al structure were fabricated in a N₂ filled glove box. Current density–voltage characterization of the devices showed that the solar cells with PbS nanorods hybrid with MDMO-PPV as active layer were better in performance than the devices with the polymer only.     

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.     

一种印刷型薄膜太阳能电池p-n结调制技术

能带值为0.5~0.85 eV材料的稀缺是多结太阳能电池面临的一个主要挑战,本文使用非真空的机械化学法合成了能带值为0.83 eV的Cu₂SnS₃化合物,使用印刷技术将其制备成吸收层薄膜,并采用superstrate太阳能电池结构(Mo/Cu₂SnS₃/In₂S₃/TiO₂/FTO glass)对其光伏特性进行了研究.实验表明所制备的太阳能电池短路电流密度、开路电压、填充因子和转换效率分别为12.38 mA/cm²、320 mV、0.28和1.10%.此外,为更好地满足多结太阳能电池对电流匹配的需求,本文对所制备太阳能电池的Cu₂SnS₃/In₂S₃ p-n结进行了分析.通过在p-n结界面植入一层薄的疏松缓冲层,使调制后的太阳能电池短路电流密度从最初的12.38 mA/cm²增加到了23.15 mA/cm²,相应太阳能电池转换效率从1.1%增加到了1.92%.该p-n调制技术对印刷型薄膜太阳能电池具有重要借鉴意义.     

Carbon@SnS<Subscript>2</Subscript> core-shell microspheres for lithium-ion battery anode materials

A novel unique C@SnS₂ core-shell structure composites consisting of well-dispersity carbon microspheres and ultrathin tin disulfide nanosheets were successfully synthesized for the first time through a simple solvothermal method. The thin SnS₂ nanosheets grew onto the carbon microspheres surfaces perpendicularly and formed the close-knit porous structure. When it was used as anode materials for lithium-ion batteries, the hybrid C@SnS₂ core-shell structure composites showed a remarkable electrochemical property than pure SnS₂ nanosheets. Typically, the hybrid composites with SnS₂ nanosheet shells and carbon microsphere’s core exhibited an excellent initial discharge capacity of 1611.6 mAh/g. Moreover, the hybrid composites exhibited capacities of 474.8–691.6 mAh/g at 100 mA/g over 50 battery cycles, while the pure SnS₂ could deliver capacities of 243–517.6 mAh/g in the tests. The results indicated that the improvement of lithium storage performance of the core-shell structure C@SnS₂ anode materials in terms of rate capability and cycling reversibility owing to the introduction of the smooth carbon microspheres and special designing of core-shell structure.     

连续离子层吸附反应沉积后硫化法制备柔性铜锌锡硫薄膜太阳电池

在柔性钼箔衬底上采用连续离子层吸附反应法(successive ionic layer absorption and reaction)制备ZnS/Cu2SnSx叠层结构的预制层薄膜,预制层薄膜在蒸发硫气氛、550 C温度条件下进行退火得到Cu2ZnSnS4吸收层.分别采用EDS,XRD,Raman,SEM表征吸收层薄膜的成分、物相和表面形貌.结果表明,退火后薄膜结晶质量良好,表面形貌致密.用在普通钠钙玻璃上采用相同工艺制备的CZTS薄膜表征薄膜的光学和电学性能,表明退火后薄膜带隙宽度为1.49 eV,在可见光区光吸收系数大于104cm 1,载流子浓度与电阻率均满足薄膜太阳电池器件对吸收层的要求.用上述柔性衬底上的吸收层制备Mo foil/CZTS/CdS/i-ZnO/ZnO:Al/Ag结构的薄膜太阳电池得到2.42%的效率,是目前报道柔性CZTS太阳电池最高效率.     

Microwave-assisted rapid synthesis of tetragonal Cu2SnS3 nanoparticles for solar photovoltaics

A simple and rapid process for the synthesis of Cu₂SnS₃ (CTS) nanoparticles by microwave heating of metal–organic precursor solution is described. X-ray diffraction and Raman spectroscopy confirm the formation of tetragonal CTS. X-ray photoelectron spectroscopy indicates the presence of Cu, Sn, S in +1, +4, ?2 oxidation states, respectively. Transmission electron microscopy divulges the formation of crystalline tetragonal CTS nanoparticles with sizes ranging 2–25 nm. Diffuse reflectance spectroscopy in the 300–2,400 nm wavelength range suggests a band gap of 1.1 eV. Pellets of CTS nanoparticles show p-type conduction and the carrier transport in temperature range of 250–425 K is thermally activated with activation energy of 0.16 eV. Thin film solar cell (TFSC) with architecture: graphite/Cu₂SnS₃/ZnO/ITO/SLG is fabricated by drop-casting dispersion of CTS nanoparticles which delivered a power conversion efficiency of 0.135 % with open circuit voltage, short circuit current and fill factor of 220 mV, 1.54 mA cm^?2, 0.40, respectively.     

Investigation of polymer/inorganic hybrid photovoltaic device using quantum dots as the interface modifier

CdS quantum dots (QDs) were introduced as an interface modifier in the poly(3-hexylthiophene) (P3HT)/TiO₂ nanorod arrays hybrid photovoltaic device. The presence of CdS QDs interlayer was found to provide enhanced light absorption, increased interfacial recombination resistance at the P3HT/TiO₂ interfaces, thus leading to a lower recombination rate of the electrons due to the stepwise structure of band edge in P3HT/CdS/TiO₂, which accounts for the observed enhanced photocurrent and photovoltage of the hybrid solar cells. The optimized performance was achieved in P3HT/CdS/TiO₂ hybrid solar cells after deposition of CdS QDs for 10 cycles, with a power conversion efficiency of 0.57 %, which is nearly ten times higher than that of P3HT/TiO₂. The findings indicate that inorganic semiconductor quantum dots provide effective means to improve the performance of polymer/TiO₂ hybrid solar cells.     

The effect of sulphur amount in sulphurization stage on secondary phases in Cu2SnS3(CTS) films

Cu₂SnS₃ is a promising absorber for green thin film solar cells because of its suitable optoelectrical properties and environment friendly components. In this study, CTS films were prepared by sulphurization of stacked metallic precursors deposited by thermal evaporation. Some physical properties were investigated by changing the amount of sulphur used in sulphurization stage. Highly crystalline tetragonal-CTS phase was obtained for all samples. However, Cu₃SnS₄ and CuS secondary phases were also determined at low amounts. Cu/Sn ratio approached to desired stoichiometry of CTS with increasing sulphur amount. Absorption spectra showed that there are two discrete absorption regions that are related to tetragonal-CTS and secondary phases. Thickness and optical constants were determined using spectroscopic ellipsometry. Atomic force microscope was used to evaluate the effects of sulphur amount on the morphology of CTS films. As a result, this study suggests a way of minimizing the secondary phases to obtain single phase tetragonal CTS.     

Search for radiation damage in heavy ion implanted thin layer single crystal SnS22

Single crystal platelets of stannic sulfide (SnS₂, trigonal) mounted with the easy cleavage plane normal to the incident ion beam, were implanted at 100 K with 150 and 350 KeV O⁺ ions to a total dose of $\text{\$}\text{?}$2.5 × 10¹⁷ cm^?2, and subsequently examined by ¹¹⁹Sn Mossbauer spectroscopy in transmission geometry. Despite the expectation that a hot zone of $\text{\$}\text{?}$300 Å radius is created near the end of the ion track, no evidence for the thermal decomposition of SnS₂ to SnS + S is observed for thermally well clamped samples. Data for the lattice temperature of oxygen implanted SnS₂ are compared to that for unirradiated single crystal and randomly oriented powder samples.     

New type of inorganic–organic hybrid (heteropolytungsticacid–polyepichlorohydrin) polymer electrolyte with TiO2 nanofiller for solid state dye sensitized solar cells

A new type of inorganic–organic hybrid solid state polymer electrolyte consisting of heteropolytungsticacid impregnated polyepichlorohydrin with iodine/iodide and TiO₂ nanofiller have been prepared for their potential application in dye sensitized solar cells. The prepared polymer electrolytes were well characterized by FT-IR, Scanning electron microscopy (SEM), X-ray diffraction (XRD), Electrochemical Impedance analysis (EIS) and Thermal analysis (TGA). The prepared polymer electrolyte with TiO₂ nanofiller shows reasonable ionic conductivity (20.4 × 10⁻⁶ S cm⁻¹) compared to pure polyepichlorohydrin (2.0 × 10⁻⁹ S cm⁻¹) at ambient temperature. The presence of negatively charged redox species heteropolytungsticacid in the polymer matrix prevents the photo reduction of iodide (back electron transfer) and the presence of TiO₂ nanofiller increases the degree of amorphousity of the polymer which in turn prolongs the stability of the fabricated dye sensitized solar cell over a long period compared to bare polymer electrolyte.     

Ferromagnetic spin-order in Mg-doped SnS2 nanoflowers prepared by hydrothermal method

Mg-doped SnS₂ nanoflowers were synthesized by hydrothermal method. The XRD and absorption spectra analyses reveal that the incorporated Mg atoms substitute for Sn atoms in SnS₂ lattice and red-shift the band-gap at low doping concentration (≤4 at%). With further doping, a transformation of Mg atoms from substitutional sites to interstitial sites occurs. The ferromagnetism of SnS₂ nanoflowers is enhanced non-monotonously with Mg doping and the largest saturation magnetization of 2.11×10⁻³ emu/g appears in 4 at% Mg-doped SnS₂. The holes created by Mg substituted incorporation may be the origin of the ferromagnetism. On the other hand, interstitial Mg atoms play a negative role in enhancing the ferromagnetism due to the holes compensation effect.     

Fabrication of ZnO and its enhancement of charge injection and transport in hybrid organic/inorganic light emitting devices

ZnO nanocrystals were synthesized by hydrolysis in methanol. X-ray diffraction and photoluminescence spectra confirm that good crystallized ZnO nanoparticles were formed. Utilizing those ZnO nanoparticles and poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV), light emitting devices with indium tin oxide (ITO)/poly(3,4-oxyethyleneoxy-thiophene):poly(styrene sulfonate) (PEDOT:PSS)/ZnO:MDMO-PPV/Al and ITO/PEDOT:PSS/MDMO-PPV/Al structures were fabricated. Electroluminescence (EL) spectra reveal that EL yield of hybrid MDMO-PPV and ZnO nanocrystals devices increased greatly as compared with pristine MDMO-PPV devices. The current-voltage characteristics indicate that addition of ZnO nanocrystals can facilitate electrical injection and charge transport. The decreased energy barrier to electron injection is responsible for the increased efficiency of electron injection.     

Sonochemical preparation of SnS and SnS2 nano- and micropowders and their characterization

Sonochemical production of tin(II) and tin(IV) sulfides is investigated. Different conditions of syntheses are examined: used solvent (ethanol or ethylenediamine), source of tin (SnCl₂ or SnCl₄), the molar ratio of thioacetamide to the tin source, and time of sonication. The obtained powders are characterized by the X-ray diffraction method (PXRD), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX), and the Tauc method. Raman and FT-IR measurements were performed for the obtained samples, which additionally confirmed the crystallinity and phase composition of the samples. The influence of experimental conditions on composition (is it SnS or SnS₂), morphology, and on the bandgap of obtained products is elucidated. It was found that longer sonication times favor more crystalline product. Each of bandgaps is direct and most of them show typical values – c.a. 1.3 eV for SnS and 2.4 eV for SnS₂. However, there are some exceptions. Synthesized powders show a variety of forms such as needles, flower-like, rods, random agglomerates (SnS₂) and balls (SnS). Using ethanol as a solvent led to powders of SnS₂ independently of which tin chloride is used. Sonochemistry in ethylenediamine is more diverse: this solvent protects Sn²⁺ cations from oxidation so mostly SnS is obtained, while SnCl₄ does not produce powder of SnS₂ but Sn(SO₄)₂ instead or, at a higher ratio of thioacetamide to SnCl₄, green clear mixture.     

Phase relations and optical properties of semiconducting ternary sulfides in the system Cu–Sn–S

The ternary system Cu–Sn–S was re-investigated and the phase diagram Cu₂S–SnS₂ studied in detail by differential thermal analysis and X-ray diffractometry. Three phases of composition Cu₄SnS₄, Cu₂SnS₃ and Cu₂Sn_3+xS_7+2x(0≤×≤1) were found exhibiting melting points at 833, 856 and 803 °C, respectively. Ellipsometric and diffuse reflectance measurements revealed that the latter two sulfides possess a fundamental band gap of 0.93 eV followed by a higher transitions. For the first time it could be demonstrated that Cu₂Sn₃S₇ has semiconducting properties and an absorption coefficients of the order 10⁵ cm⁻¹.     

Structural and electrical studies on PVDF:PANI composite thin films and their application as buffer layer on hybrid solar cells

Hybrid (organic–inorganic) solar cells were fabricated and tested using buffer layer of polyaniline (PANI)–poly(vinylidene difluoride) (PVDF) composites. The effect of PANI:PVDF composite on the performance of the solar cells was explored and the cells were characterized by current voltage (I?V) measurements under a solar simulator generating AM1.5 light (1000?W/m²) irradiance. It was found that solar cells containing ITO/PANI:PVDF photo-anode are likely to improve photocurrent and power conversion efficiency in a way superior to that containing only ITO as photo-anode. Furthermore, PANI:PVDF composite enhanced the hole extraction at photo-anode/photo-active layer interface via the high electrical conductivity of PANI and the ferroelectricity of PVDF.     

Study on the photovoltaic property of Cu4SnS4 synthesized by mechanochemical process

Photovoltaic property of Cu₄SnS₄ (CTS) is studied by employing a superstrate solar cell structure of Mo/CTS/In₂S₃/TiO₂/fluorine-doped tin oxide (FTO) glass for the first time. The CTS absorber layer was prepared by a combination of mechanochemical and doctor blade processes. The annealing effects on the structural, optical and electronic properties of the CTS absorber layer were investigated. The novel CTS absorber layer shows conversion efficiency as high as 2.34% under the standard AM 1.5 condition.     

Synthesis of earth-abundant Cu2SnS3 powder using solid state reaction

Cu₂SnS₃ (CTS) powder has been synthesized at 200 °C by solid state reaction of pastes consisting of Cu and Sn salts and different sulphur compounds in air. The compositions of the products is elucidated from XRD and only thiourea is found to yield CTS without any unwanted CuS_x or SnS_y. Rietveld analysis of Cu₂SnS₃ is carried out to determine the structure parameters. XPS shows that Cu and Sn are in oxidation states +1 and +4, respectively. Morphology of powder as revealed by SEM shows the powder to be polycrystalline with porous structure. The band gap of CTS powder is found to be 1.1 eV from diffuse reflectance spectroscopy. Cu₂SnS₃ pellets are p-type with electrical conductivity of 10⁻² S/cm. The thermal degradation and metal–ligand coordination in CTS precursor are studied with TGA/DSC and FT-IR, respectively, and a probable mechanism of formation of CTS has been suggested.     

g-C3N4/SnS2异质结构:一类有潜力的光解水催化剂

采用第一性原理方法研究了层间耦合作用对g-C₃N₄/SnS₂异质结构的电子结构和吸光性质的影响.发现g-C₃N₄/SnS₂是一类典型的范德瓦异质结构,能有效吸收可见光,其价带顶和导带底与水的氧化还原势匹配,且由于电荷转移而导致的界面处极化场有利于光生载流子的分离.这些理论研究结果表明g-C₃N₄/SnS₂异质结构是一类非常有潜力的光解水催化材料.     

A theoretical study on tuning band gaps of monolayer and bilayer SnS2 and SnSe2 under external stimuli

Based on density functional theory, we systematically study the mechanical and electronic properties of monolayer and bilayer SnS₂ and SnSe₂. The electronic properties of these layers can be significantly tuned by applying in-plane strains and electric fields perpendicular to the sheets. The band gaps of monolayer SnS₂ and SnSe₂ slightly increase with the in-plane tensile strains, and they start to decrease after critical strains (5% for monolayer SnS₂ and 7% for monolayer SnSe₂). The band gaps of bilayer SnS₂ and SnSe₂ have a similar tendency to the monolayers with smaller critical strains (1% for bilayer SnS₂ and 2% for bilayer SnSe₂), which enables a semiconductor-to-metal transition at 10% strain for bilayer SnSe₂. We also find that an external electric field perpendicular to bilayer SnS₂ and SnSe₂ modulates their electronic band gaps. Semiconductor-to-metal transitions are achieved at the electric fields of 0.27 V/Å for bilayer SnS₂ and 0.13 V/Å for bilayer SnSe₂.     

Mobility of electrons in SnS2−xSex

The electrical resistivities and Hall constants of the semiconducting compounds SnS_2?xSe_x have been measured at temperatures ranging from 100 to 450 K and three donor ionization energies (0.013, 0.086 and 0.25 eV) have been identified. The Hall mobilities exhibit for T> 200K a temperature dependence of the form μ～ (T/T₀)^?n separating the SnS_2?xSe_x compounds into two groups one behaving like SnS₂ and the other like SnSe₂.