Fabrication of Cu2ZnSn(SxSe1−x)4 thin film solar cell by single step sulfo-selenization of stacked metallic precursors

We have synthesized an efficient Cu₂ZnSn(S_xSe_1−x)₄ (CZTSSe) absorbers by using single-step rapid thermal sulfo-selenization process of sputtered stack metallic precursor (Zn/Sn/Cu) films. The structural and morphological studies confirm that the suitability of the rapid thermal sulfo-selenization process for the synthesis of a CZTSSe absorber without any secondary phases with large grains. The annealing atmosphere with a mixed-chalcogen source enhances the grain growth of the CZTSSe absorber as compared with pure Cu₂ZnSnS₄ (CZTS) and Cu₂ZnSnSe₄ (CZTSe) absorbers. The CZTSSe thin film solar cell shows the best conversion efficiency of ∼7%.     

Application of multi-buffer layer of (Zn,Mg)O/CdS in Cu2ZnSn(S,Se)4 solar cells

(Zn,Mg)O (ZMO) buffer layer has attracted attention for having the potential to control the conduction band offset of buffer layer and large band-gap (Eg) Cu₂ZnSn(S,Se)₄ (CZTSSe) absorber interface, where the ZMO layer is deposited by the sputtering. However, the solar cell efficiency is decreased with the ZMO layer as compared with the CdS layer. The decrease in conversion efficiency is attributed to the sputtering damage on the absorber and high light reflection from the surfaces of CZTSSe solar cells. To completely suppress the damage, a CdS layer with very thin thickness of 20 nm is inserted between the ZMO layer and the CZTSSe layer. In addition, MgF₂ layers are deposited on CZTSSe solar cells as anti-reflection coating. Ultimately, the solar cell with multi-buffer layer of ZMO/thin-CdS is almost same level as that with the CdS layer. Therefore, the multi-buffer layer can be an appropriate buffer layer of the large-Eg CZTSSe layer.     

太阳电池用Cu2ZnSnS4薄膜的反应溅射原位生长及表征

通过直流反应磁控溅射技术,原位生长制备了太阳电池用Cu₂ZnSnS₄(CZTS)薄膜.采用X射线能量色散谱仪、扫描电镜、X射线衍射仪、紫外可见分光光度计和霍尔效应测试系统对薄膜进行了表征.结果表明,原位生长的CZTS薄膜具有均质、致密和平整的形貌,且由贯穿整个薄膜厚度的柱状颗粒组成.不同基底温度下生长所得薄膜的Cu/(Zn+Sn) 值均约为1,而Zn/Sn值均大于1且随着基底温度升高而减小.所得薄膜在(112)方向上择优取向明显,且结构特征受基底温度和Cu/(Zn+Sn)的共同影响.所得薄膜均具有高达10⁴cm^-1的光吸收系数,其带隙宽度随着生长温度的增加而降低,并且在500℃时为(1.51±0.01)eV.薄膜的导电类型均为p型,且具有与器件级Cu(In,Ga)Se₂(CIGS)相当的载流子浓度. 关键词： 2ZnSnS₄')" href="#">Cu₂ZnSnS₄ 直流反应磁控溅射 原位生长 太阳电池     

Comparative study on Cu2ZnSn(S,Se)4 based thin film solar cell performances by adding various back surface field (BSF) layers

In this research work, SCAPS-1D (Solar Cell Capacitance Simulator in one Dimension) is used to simulate the CZTSSe (Cu2ZnSn(S,Se)4) solar cell with Al/ZnO:Al/ZnO(i)/CdS/CZTSSe/Mo structure. The simulation results have been compared and validated with real experimental results. After that, an effective receipt is proposed with the aim of improving the efficiency of the CZTSSe solar cell, in which a BSF layer is inserted using various materials (SnS, CZTSSe and CZTSe). The obtained results show that the efficiencies of CZTSSe solar cells are increased from 12.3% to 15.7%, 15.3% and 15% by the insertion of SnS, CZTSSe and CZTSe materials as BSF layers, respectively. This enhancement corresponds with a BSF layer thickness of 30 nm and doping concentration of 1E18 cm⁻³. Next, an optimization of BSF layers thickness has been conducted. The optimum value of thickness is considered at 40 nm with an enhancement ratio in efficiency of 36.70%, 26.21% and 21.53% for SnS, CZTSSe and CZTSe, respectively. Better performances have been noted for SnS material. The optimized CZTSSe solar cell with SnS as a BSF layer achieves an efficiency of 16.95% with J_SC = 36.34 mA/cm², V_OC = 0.69 V, and FF = 67% under Standard Test Conditions (AM1.5 G and cell temperature of 25 °C).     

A study of the microstructure,thermal properties and wetting kinetics of Sn–3Ag–<Emphasis Type="Italic">x</Emphasis>Zn lead-free solders

Microstructure, thermal properties and wetting kinetics of Sn–3Ag–xZn solders (x = 0.4, 0.6, 0.8, 1, 2 and 4 wt%) were systematically investigated. The results indicate that a small amount of Zn (Zn wt% ≤ 1 wt%) has a rather moderate effect on the microstructure morphology of the Sn–3Ag–xZn solders. The microstructures are composed of a β-Sn phase and the mixture of Ag₃Sn and ζ-AgZn particles. However, the β-Sn phase reduces its volume fraction in the entire microstructure and the intermetallic compounds population increases with the increasing of Zn content. The microstructure is dramatically changed with a further increase in the Zn content. The γ-AgZn phase is formed in a Sn–3Ag–2Zn solder. The ε-AgZn phase is formed in a Sn–3Ag–4Zn solder. The melting temperature and the undercooling of the Sn–3Ag–xZn solder alloys decrease with the increase in Zn content, reach to a minimum value when the content of Zn is 1 wt%, and then increase with further increase in Zn content. The Sn–3Ag–1Zn demonstrates the minimum value of 228.13 °C in the melting temperature and 13.87 °C in undercooling. The wetting kinetics of the main spreading stage features the power law of R ⁿ  ~ t (n = 1), which is controlled by chemical reactions at the triple line.     

Precisely tuning Ge substitution for efficient solution-processed Cu_2ZnSn(S,Se)_4 solar cells

The kesterite Cu_2ZnSn(S,Se)_4(CZTSSe) solar cells have yielded a prospective conversion efficiency among all thinfilm photovoltaic technology. However, its further development is still hindered by the lower open-circuit voltage(Voc), and the non-ideal bandgap of the absorber is an important factor affecting this issue. The substitution of Sn with Ge provides a unique ability to engineer the bandgap of the absorber film. Herein, a simple precursor solution approach was successfully developed to fabricate Cu_2Zn(SnyGe_(1-y))(SxSe_(1-x))_4(CZTGSSe) solar cells. By precisely adjusting the Ge content in a small range, the V_(oc) and J_(sc) are enhanced simultaneously. Benefitting from the optimized bandgap and the maintained spike structure and light absorption, the 10% Ge/(Ge+Sn) content device with a bandgap of approximately 1.1 eV yields the highest efficiency of 9.36%. This further indicates that a precisely controlled Ge content could further improve the cell performance for efficient CZTGSSe solar cells.     

间隙原子对ZnNb2O6光电特性影响的第一性原理研究

基于密度泛函理论第一性原理，研究Zn、Nb、O间隙原子对ZnNb₂O₆体系光电特性的影响。分析显示：间隙原子对体系晶格畸变的影响与间隙原子几何尺寸有关。缺陷结构中，由于间隙原子电负性存在差异，也是产生晶格畸变的因素。光电特性分析显示：含有Zn、Nb间隙原子的体系表现为n型简并半导体。且Nb_i表现出较强的介电效应，主要与Nb的离子势与电离能有关。O_i表现为p型简并半导体，对光电效应贡献较小。结果表明Nb_i体系有良好的光电特性，在实际应用中具有较大潜力。     

Properties of Cu2ZnSn(SxSe1−x)4 thin films prepared by one-step sulfo-selenization of alloyed metal precursors

The pentenary system, Cu₂ZnSn(S_xSe_1−x)₄ (CZTSSe), is a promising alternative for thin film solar cells. In this study, CZTSSe thin films were prepared using a two-stage process involving the thermal diffusion of sulfur (S) and selenium (Se) vapors into sputtered metallic precursors at approximately 450 °C. The effects of the sulfur content on the composition, structure, optical and electrical characteristics of the CZTSSe thin films were investigated. The films showed a kesterite structure with a predominant (112) orientation. X-ray diffraction and Raman spectroscopy confirmed the formation of a single phase CZTSSe compound. The band gap was dependent on the sulfur content and was calculated to be 1.25 eV, 1.33 eV and 1.40 eV for CZTSSe films with a S/(S + Se) ratio of 0.3, 0.5 and 0.7, respectively. All films exhibited p-type semiconductor properties.     

Iron-metal multilayers studied by Mössbauer spectroscopy,RBS and X-ray diffraction

Fe/M (M = Ag, Zn and Sn) multilayers prepared by a vacuum evaporation method are studied by Mössbauer spectroscopy (MS), Rutherford backscattering spectroscopy (RBS) and X-ray diffraction (XRD). For the case of an M = Ag multilayer, MS reveals that Fe in the multilayer remains as an-phase down to the layer thickness of 10 nm. This result is in agreement with the RBS result that Fe and Ag form a completely discrete layer structure without any mutual mixing. For the case of M = Zn and Sn, RBS reveals that a considerable mixing has taken place between Fe and Sn during the specimen preparation. MS on Fe/Sn specimens with different layer thickness shows that an alloy phase of about 5 nm thickness is formed at the interface. Structural as well as magnetic properties of the alloy phase are discussed based on MS at different temperatures and on reported results of the intermetallic compound FeSn.     

Surface tension modelling of liquid Cd–Sn–Zn alloys

The thermodynamic model in conjunction with Butler equation and the geometric models were used for the surface tension calculation of Cd–Sn–Zn liquid alloys. Good agreement was found between the experimental data for limiting binaries and model calculations performed with Butler model. In the case of ternary alloys, the surface tension variation with Cd content is better reproduced in the case of alloys lying on vertical sections defined by high Sn to Zn molar fraction ratio. The calculated surface tension is in relatively good agreement with the available experimental data. In addition, the surface segregation of liquid ternary Cd–Sn–Zn and constituent binaries has also been calculated.     

Cu2ZnSn(S1–xSex)4 thin film solar cells prepared by water‐based solution process

The kesterite Cu₂ZnSn(S_1–xSe_x)₄ (CZTSSe) thin film solar cell has been developed rapidly due to its excellence in structural and optical properties and its abundance in raw materials. Both vacuum‐based and solution‐based methods have been successfully employed to fabricate CZTSSe thin film solar cells. In this Letter, we report an environmentally friendly, water‐based, solution process for fabrication of high‐efficiency CZTSSe thin film solar cells. High quality CZTSSe thin film is obtained by selenization under high temperature and Se vapor. An efficiency of 6.2% is achieved on CZTSSe thin film solar cell fabricated by such water‐based solution process. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

In掺杂ZnO薄膜的制备及其白光发射机理

采用溶胶-凝胶法在Si衬底上制备了本征ZnO薄膜和In:(Zn+In)分别为5%,8%,10%的ZnO薄膜,对薄膜的晶相结构和光电性质进行了表征并在CIE-XYZ表色系统中计算了不同样品的色品坐标.结果表明:In掺入后ZnO薄膜的择优生长方向由(002)面变为(101)面且面间距变小,当In掺杂量为5%时,In原子完全替代Zn原子;薄膜的电阻率随In含量的增加出现先抑后扬的趋势;随着In的掺入光谱的紫外发射峰红移,并在670 nm左右出现一个新的峰值;In:(Zn+In)为5%样品具有白光发射特性.从第一 关键词： In掺杂ZnO薄膜 溶胶-凝胶 色品坐标 白光发射     

部分阳离子取代优化铜锌锡硫硒薄膜太阳能电池性能研究进展

作为无机化合物薄膜太阳能电池中具有代表性的一类电池,铜锌锡硫硒(Cu2ZnSn(S,Se)4,简称CZTSSe)薄膜太阳能电池因其组成元素地壳含量丰富、低毒等优点受到广泛关注.目前,吸收层的高缺陷密度和器件的低开路电压被认为是限制该类电池效率的两个关键因素.为了突破这两大困境,科研人员发展了阳离子取代方法,即通过引入其...     

The characteristic of Cu2ZnSnS4 thin film solar cells prepared by sputtering CuSn and CuZn alloy targets

Recent study shows that the main reason for limiting CZTS device performance lies in the low open circuit voltage, and crucial factor that could affect the V_oc is secondary phases like ZnS existing in absorber layer and its interfaces. In this work, the Cu₂ZnSnS₄ thin film solar cells were prepared by sputtering CuSn and CuZn alloy targets. Through tuning the Zn/Sn ratios of the CZTS thin films, the crystal structure, morphology, chemical composition and phase purity of CZTS thin films were characterized by X-Ray Diffraction (XRD), scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS) and Raman spectroscopy. The statistics data show that the CZTS solar cell with a ratio of Zn/Sn = 1.2 have the best power convention efficiency of 5.07%. After HCl etching process, the CZTS thin film solar cell with the highest efficiency 5.41% was obtained, which demonstrated that CZTS film solar cells with high efficiency could be developed by sputtering CuSn and CuZn alloy targets.     

Electrochemical deposition of quaternary Cu2ZnSnS4 thin films as?potential solar cell material

Quaternary compound semiconductor Cu₂ZnSnS₄ (CZTS), which appears to be a promising candidate for the absorber of a thin film type solar cell, was grown on polycrystalline Ag substrates by electrochemical epitaxial method. The elements were deposited in the following sequence: S/Sn/S/Cu/S/Zn/S/Cu… , the order being one cycle of SnS, one cycle of ZnS and two cycles of CuS. Morphology of the deposit has been characterized by field emission scanning electron microscopy (FE-SEM) with an energy dispersive X-ray (EDX) analyzer. X-ray diffraction (XRD) studies showed a (112) preferred orientation for the deposit. X-ray photoelectron spectroscopy (XPS) of the deposit indicated an approximate ratio 2:1:1:4 of Cu, Zn, Sn, and S, the expected stoichiometry for the deposit, and similar results have been obtained from EDX data. Near IR absorption measurements of the deposit at room temperature indicated a direct band gap of 1.5 eV, and open-circuit potential (OCP) studies indicated a good p-type property, both of which were suitable for fabricating a thin film solar cell.     

Laboratory tests of low density astrophysical nuclear equations of state

Clustering in low density nuclear matter has been investigated using the NIMROD multidetector at Texas A&M University. Thermal coalescence modes were employed to extract densities, ρ, and temperatures, T, for evolving systems formed in collisions of 47A MeV (40)Ar+(112)Sn, (124)Sn and (64)Zn+(112)Sn, (124)Sn. The yields of d, t, (3)He, and (4)He have been determined at ρ=0.002 to 0.03 nucleons/fm(3) and T=5 to 11 MeV. The experimentally derived equilibrium constants for α particle production are compared with those predicted by a number of astrophysical equations of state. The data provide important new constraints on the model calculations.     

Structure Evolution and Diffusion During Interphase Boundary Sliding in Binary Eutectics Based on Sn

Mechanical behaviour of interphase boundaries (IB) and microstructure in the binary eutectics (Al–Sn, Zn–Sn, Pb–Sn, Cd–Sn) heavily deformed by different schemes and regimes have been investigated. Experiments were carried out on the atomically clean surfaces of alloys and on the bimetallic joints with clean interfaces used as a macromodel of deformed IB. It has been shown that for the eutectics with high IB energy (Al–Sn, Zn–Sn) the interphase boundary sliding (IBS) occurs by means of the dislocation gliding, followed by a remarkable strengthening and accompanied by the formation of narrow stable IB cracks with sharp angles. For eutectics Pb–Sn and Cd–Sn with low IB energy, the IBS occurs as viscous flow and is accompanied by a correlated diffusion along IB. The softening of IB was observed. Intensity of development of the diffusion-controlled accommodation processes on IB depends on the extent of preliminary deformation and values of IB energy.     

Reducible and non-reducible defect clusters in tin-doped indium oxide

Density functional theory calculations are used to estimate the energy of interstitial oxygen (O_i) released from tin-doped indium oxide (ITO). The currently accepted explanation of defect clusters’ irreducibility is based on different arrangements of doping atoms around O_i. In the present contribution we demonstrate that this concept has only a limited domain of applicability and explains the relative stability of different defect clusters with the same and fixed Sn:O_i ratio. To describe practically the important case of ITO treatment under strong reduction conditions another limiting case of varying Sn:O_i ratio is considered. It is found that in this particular case local coordination of doping atoms around O_i plays only a minor role. The relative stability of the oxidized defect clusters has caused a noticeable change in the electronic part of the defect formation energy, i.e. the chemical potential of the conduction electrons determines the equilibrium concentration of the interstitial oxygen atoms.     

Nanosecond laser ablation and deposition of silver,copper, zinc and tin

Nanosecond pulsed laser deposition of different metals (Ag, Cu, Sn, Zn) has been studied in high vacuum at a laser wavelength of 355 nm and pulse length of 6 ns. The deposition rate is roughly similar for Sn, Cu and Ag, which have comparable cohesive energies, and much higher for the deposition of Zn which has a low cohesive energy. The deposition rate for all metals is strongly correlated with the total ablation yield, i.e., the total mass ablated per pulse, reported in the literature except for Sn, for which the deposition rate is low, but the total ablation yield is high. This may be explained by the continuous erosion by nanoparticles during deposition of the Sn films which appear to have a much rougher surface than those of the other metals studied in the present work.     

Sn doping effects on the electro-optical properties of sol gel derived transparent ZnO films

Undoped and tin (Sn) doped ZnO films have been deposited by sol gel spin coating method. The Sn/Zn nominal volume ratio was 1, 3 and 5% in the solution. The effect of Sn incorporation on structural and electro-optical properties of ZnO films was investigated. All the films have polycrystalline structure, with a preferential growth along the ZnO (002) plane. The crystallite size was calculated using a well-known Scherrer's formula and found to be in the range of 26-16 nm. X-ray diffraction patterns of the films showed that Sn incorporation leads to substantial changes in the structural characteristics of ZnO films. The SEM measurements showed that the surface morphology of the films was affected from the Sn incorporation. The highest average optical transmittance value in the visible region was belonging to the undoped ZnO film. The optical band gap and Urbach energy values of these films were determined. The absorption edge shifted to the lower energy depending on the Sn dopant. The shift of absorption edge is associated with shrinkage effect. The electrical conductivity of the ZnO film enhanced with the Sn dopant. From the temperature dependence of conductivity measurements, the activation energy of ZnO film increased with Sn incorporation.