阳离子部分取代Cu2ZnSnS4的研究进展

P型半导体Cu_2ZnSnS_4(CZTS)由于具有最佳的直接带隙(1.0~1.5eV)、高的光吸收系数(超过104 cm~(-1))以及丰富、无毒的元素组成,使其成为商业化低成本太阳能电池最有希望的候选材料之一。然而,材料本身的一些缺陷制约了CZTS薄膜太阳能电池效率的提高。为了提高CZTS薄膜太阳能电池的效率,研究者们使用其他阳离子部分取代Cu、Zn或Sn来改善CZTS的缺陷。从CZTS的3种不同取代位置出发,综述了近年来各种阳离子部分取代CZTS的研究进展,同时对阳离子部分取代CZTS材料的发展前景进行了展望。     

Application of Taguchi approach to optimize the sol–gel process of the quaternary Cu2ZnSnS4 with good optical properties

Present research deals with the optimal deposition parameters configuration for the synthesis of Cu₂ZnSnS₄ (CZTS) thin films using the sol–gel method associated to spin coating on ordinary glass substrates without sulfurization. The Taguchi design with a L9 (3⁴) orthogonal array, a signal-to-noise (S/N) ratio and an analysis of variance (ANOVA) are used to optimize the performance characteristic (optical band gap) of CZTS thin films. Four deposition parameters called factors namely the annealing temperature, the annealing time, the ratios Cu/(Zn + Sn) and Zn/Sn were chosen. To conduct the tests using the Taguchi method, three levels were chosen for each factor. The effects of the deposition parameters on structural and optical properties are studied. The determination of the most significant factors of the deposition process on optical properties of as-prepared films is also done. The results showed that the significant parameters are Zn/Sn ratio and the annealing temperature by applying the Taguchi method.     

A review on growth optimization of spray pyrolyzed Cu2ZnSnS4 chalcogenide absorber thin film

The progress of solar cell technology in the development of clean and economic quaternary compound copper zinc tin sulfide (CZTS)‐based absorber thin films using the spray pyrolysis technique are presented in this review. CZTS (Cu₂ZnSnS₄) is the only potential competitor for the existing solar thin film absorbing materials owing to its environment‐friendly Earth abundant constituents. Even though different nonvacuum thin film technologies have been developed for the large area fabrication of this nontoxic absorber material, spray pyrolysis technique offers more versatility in changing the process parameters which has a direct impact on the cell efficiency. It can be used for depositing a wide variety of materials even with complex composition with good crystallinity, and the method has the advantage of being flexible and straightforward to design and can be quickly adopted for extensive area deposition. A survey on the effects of experimental conditions as well as the nature of precursors on the structural, morphological, electrical, and optical properties on the spray pyrolyzed CZTS thin films is discussed in detail. This analysis certainly could provide a potential to obtain new insights in the fabrication of high‐efficiency CZTS‐based solar cells and to launch it into the commercial market to satisfy the ever‐growing future energy demand.     

Photocatalytic degradation of RhB and TNT and photocatalytic water splitting with CZTS microparticles

Cu₂ZnSnS₄ (CZTS) is a main candidate material for solar energy conversion through both photovoltaics and photocatalysis based on environmentally friendly elements and with a direct band gap of 1.5 eV. We report the synthesis of quasi Cu₂ZnSnS₄ microparticles with unprecedented narrow size distributions. The structural, morphological and core level analysis has been carried out by XRD, SEM and XPS techniques. These microparticles have shown excellent photocatalytic activity toward degradation of Rhodamine B dye (RhB) and TNT under visible light. The extent of mineralization has been analyzed by COD and TOC values. Photocatalytic water splitting for H₂ generation has also been reported.     

Improving the photovoltaic performance of co‐evaporated Cu2ZnSnS4 thin‐film solar cells by incorporation of sodium from NaF layers

We have investigated the influence of sodium (Na) on the properties of co‐evaporated Cu₂ZnSnS₄ (CZTS) layer microstructures and solar cells. The photovoltaic performance and diode properties were improved by incorporating Na from NaF layers into the CZTS layers, while Na had a negligible effect on the microstructural properties of the layer. The best cell fabricated by using an optimal CZTS layer (Cu/(Zn + Sn) = 0.70, Zn/Sn = 1.8) yielded an active area efficiency of 5.23%. The analysis of device properties suggests that charge‐carrier recombination at CZTS/CdS interface is suppressed by intentional Na incorporation from NaF layers. Copyright © 2016 John Wiley & Sons, Ltd.     

Mg掺杂Cu2ZnSnS4的第一性原理研究

采用基于密度泛函理论(DFT)的第一性原理对光伏材料Cu₂ZnSnS₄ (CZTS)掺Mg进行了研究。通过建立Mg取代CZTS中Cu、Zn和Sn的点缺陷结构, 计算Mg掺杂缺陷的生成能及对CZTS电子结构的影响。计算结果表明掺Mg不引入深能级缺陷也不改变材料的禁带宽度; 并且富Sn条件更有利于Mg取代Cu形成施主缺陷, 使p型转变为n型。本研究可为CZTS太阳能电池掺Mg的应用研究提供理论基础。     

Electrical properties of Cu4ZnSnS2/ZnS heterojunction prepared by ultrasonic spray pyrolysis

Cu₂ZnSnS₄ (CZTS)/ZnS heterojunctions have been prepared by a successive deposition of ZnS and CZTS thin films by ultrasonic spray pyrolysis technique on glass substrates. The cupric chloride concentration has been varied in the starting solution in order to investigate its influence on device properties. CZTS/ZnS heterojunctions were characterized by recording their current-voltage characteristics at different temperatures. The obtained results exhibit a good rectifying behavior of the realized heterojunction. Analysis of these results yields saturation current, series resistance and ideality factor determination. From the activation energy of saturation current we inferred that the thermal emission through the barrier height is the dominant mechanism of the reverse current rather than the defects contribution.     

硫化退火温度对金属三靶顺序溅射CZTS薄膜性能的影响

通过XRD及Raman物相分析、SEM形貌观察和EDS成分分析等方法研究了硫化退火温度对金属三靶顺序溅射铜锌锡硫(CZTS)薄膜性能的影响。结果表明,在一定温度范围内(500~580℃),随着温度的升高薄膜的结晶性能有变好的趋势,形貌也得到了改善。当温度达到600℃时,CZTS薄膜会发生分解反应,该分解反应不但导致薄膜结晶性能及形貌恶化,也造成了锡元素的损失。580℃条件下获得的薄膜各项性能俱佳,是最适合本实验体系的退火温度。     

Second- and third-order elastic constants of kesterite CZTS and its electronic and optical properties under various strain rates

In this paper, the continuum approach is used to calculate the second-order elastic constants and the third-order elastic constants of the kesterite CZTS semiconductor. In this approach, by applying the various deformation types to matter and using density functional theory the energy–strain curves are plotted and the corresponding elastic coefficients are extracted. In this paper, the effect of symmetrical strains on CZTS electronic and optical properties has been investigated. For kesterite CZTS, a bandgap of about 0.2 and 1.8 eV with revised Perdew?–Burke?–Ernerhof for solids functional and HSE06 approximation, respectively, ? is obtained. This semiconductor has been conductive in tensile strains and in return, increased its bandgap in compressive strain. In addition, its bandgap becomes indirect in the strains about ?9%. Also, the first peak in the imaginary section of the dielectric function has well conformity to experimental results and its changing process can show the changing process of optical bandgap under external strains such as temperature variations and substrate mismatch.     

Influence of annealing on p-type Cu2ZnSnS4 thin film by dip coating solution growth technique for the application of solar cell

Thin films of Cu₂ZnSnS₄ have been deposited by solution growth dip coating method. Different Cu/Zn/Sn/S molar ratios were applied, which tells the properties of copper, Zinc, Tin, and Sulfide using X-ray diffraction, UV–vis, Energy dispersive X-ray spectroscopy, and scanning electron spectroscopy. The pure CZTS thin film showed the phase transformation from Kesterite (tetragonal) to Kesterite (orthorhombic) crystal structure. Optical measurement analysis reveals that layers have relatively high absorption coefficient in the visible spectrum with a band gap reduction of 1.51–1.49?eV with an increase in the annealing temperature from room temperature to 300?°C for 1?h in hot air furnace without any presence of an inert gas. Optical conductivity was observed to increase from 10¹² to 10¹³ (sec)^?1 and electrical conductivity was of the order of 10² (Ω?cm)^?1.