H2S气氛下硫化温度对Cu2ZnSnS4薄膜性能影响的研究

用磁控溅射法在玻璃衬底上沉积Zn/Sn/Cu预置层,然后再在H2S气氛下将其硫化制成Cu2ZnSnS4(CZTS)薄膜。研究了不同硫化温度(460,500,540和580℃)对CZTS薄膜性能的影响。采用X射线衍射、Raman、扫描电镜、能量色散谱和紫外-可见-近红外分光光度计表征薄膜的物相、表面形貌和光学性能。结果表明,在不同硫化温度下都成功制备了CZTS薄膜。当硫化温度为540℃时,制备的薄膜晶粒达到2μm,结晶性最好,表面致密光滑,而且它的吸收系数大于7×104cm-1,禁带宽度为1.49 e V。硫化温度较低(460℃)时,含有Cu2-xS杂质相,表面存在孔洞。而硫化温度较高(580℃)时,晶界处会产生微裂纹。     

Na2S2O3浓度对共电沉积制备Cu2ZnSnS4薄膜性能的影响

采用电化学沉积的方法在SnO2透明导电玻璃基底上沉积Cu2ZnSnS4(CZTS)薄膜,在氮气保护下对其进行进一步硫化,研究了溶液中不同Na2S2O3浓度对沉积薄膜性质的影响。运用X射线衍射、扫描电镜、紫外-可见光分光光度计和拉曼光谱等手段分别对薄膜进行表征。实验结果表明:随着浓度的增加,薄膜的结构和光学特性逐渐变好。当Na2S2O3的浓度为0.11 mol/L时,制得理想的具有类黝锡矿结构的CZTS薄膜,光学带隙1.51 eV。     

磁控溅射制备Cu2ZnSnS4薄膜的研究进展

Cu_2ZnSnS_4(CZTS)薄膜由于其合适的禁带宽度、高的光吸收系数以及组分无毒、储量丰富等特性,被视为薄膜太阳能电池最佳的吸收层材料之一。磁控溅射是制备CZTS薄膜的主要方法之一,因为其制备过程相对简单且可以产业化,一直是太阳能电池领域的研究热点。从磁控溅射制备CZTS薄膜的3种路径出发,综述了近年来各种路径在制备CZTS薄膜方面的研究进展,比较了3种路径的优缺点,同时对磁控溅射制备CZTS薄膜的发展前景进行了展望。     

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。     

溶胶-凝胶法制备CZTS太阳能电池吸收层薄膜

Cu2ZnSnS4(CZTS)具有与CIGS相似的结构,其直接带隙宽度为1.45~1.6eV,吸收系数则高于104cm-1,构成元素丰富且无毒,因此其作为一种P型半导体材料,被认为是最有希望替代CIGS的材料之一。以去离子水和无水乙醇作为溶剂,采用溶胶-凝胶法(Sol-gel)在玻璃基底上制得了CZTS薄膜,利用X射线衍射仪、拉曼光谱仪、扫描电镜和紫外可见光谱对样品进行了表征,并讨论了烘焙温度对薄膜结构和形貌的影响。结果表明当热处理温度达到200℃时得到了黑色的CZTS薄膜,其禁带宽度为1.45eV,经过EDS分析制得的薄膜的元素比Cu∶Zn∶Sn∶S接近2∶1∶1∶4,这与CZTS的理论值是一致的,但是薄膜中存在少量的氯元素,同时适当降低前期的烘焙温度可以提高薄膜的致密性。     

Cu2ZnSnS4纳米颗粒及其薄膜的制备与表征

采用热注入法,在油胺(OLA)中合成出Cu2ZnSnS4(CZTS)纳米颗粒,并在玻璃衬底上制备了薄膜,研究了不同合成温度对纳米颗粒生成的影响.通过X射线衍射仪、拉曼光谱仪、透射电子显微镜、扫描电子显微镜、紫外可见分光光度计对所得纳米晶材料的结构与成分、颗粒大小与形貌、光吸收谱进行了测试分析.研究结果表明:采用热注入法的最佳合成温度在260℃左右,该温度下生成的多晶CZTS纳米颗粒尺寸约10 nm,分散性良好,光学禁带宽度约1.5 eV.     

多周期分层溅射硫化物靶制备铜锌锡硫薄膜太阳电池EI北大核心CSCD

按照ZnS/CuS/SnS/CuS的顺序分层溅射硫化锌、硫化铜和硫化亚锡三个二元硫化物靶,制备铜锌锡硫(CZTS)的预制层。在预制层总厚度不变的情况下按照上述顺序将预制层分多个周期溅射,然后在360℃对含硫预制层进行低温退火,再在硫气氛中进行高温(600℃)硫化处理,制备出CZTS薄膜。周期数为3的CZTS薄膜表面平整致密、晶粒大小均匀,禁带宽度为1.50eV。用这种薄膜制备的CZTS薄膜太阳电池性能最好,其开路电压(Voc)为623mV,短路电流密度(Jsc)为11.79mA/cm^2,光电转换效率达到2.93%。     

合成Cu_2ZnSnS_4薄膜四元共电沉积机理与退火相转变

采用循环伏安法研究了制备CZTS薄膜四元预制层的电化学沉积机理。结合XRD,SEM,EDS和Raman技术分析预制层退火的相转变机制。结果表明:溶液中Cu2+和Sn2+浓度不仅影响其本身的沉积速率,还影响溶液中其他金属元素的沉积速率,而Zn2+浓度仅影响其本身沉积速率。四元预制层的沉积以原子层外延为机理,在负电位作用下,Cu2+先转变为Cu原子沉积在衬底表面,且与衬底附近析出的S原子发生化学反应,在衬底上生成CuS,同样,SnS和ZnS也以这种方式交替沉积在衬底上。预制层二元硫化物随着退火温度的升高逐渐转变为Cu2(3)SnS3(4)和Cu2ZnSnS4。利用四元共电沉积预制层550℃退火1h合成的Cu2ZnSnS4薄膜原子比为Cu∶Zn∶Sn∶S=23.72∶12.22∶13.07∶50.99。无偏压下合成的CZTS薄膜光电流达到约6nA。     

多周期分层溅射硫化物靶制备铜锌锡硫薄膜太阳电池

按照ZnS/CuS/SnS/CuS的顺序分层溅射硫化锌、硫化铜和硫化亚锡三个二元硫化物靶,制备铜锌锡硫(CZTS)的预制层。在预制层总厚度不变的情况下按照上述顺序将预制层分多个周期溅射,然后在360℃对含硫预制层进行低温退火,再在硫气氛中进行高温(600℃)硫化处理,制备出CZTS薄膜。周期数为3的CZTS薄膜表面平整致密、晶粒大小均匀,禁带宽度为1.50eV。用这种薄膜制备的CZTS薄膜太阳电池性能最好,其开路电压(Voc)为623mV,短路电流密度(Jsc)为11.79mA/cm~2,光电转换效率达到2.93%。     

电化学沉积法制备Cu_2ZnSnS_4薄膜电池

采用简单的两电极电化学沉积金属薄膜技术,在镀钼的钠钙玻璃衬底上共沉积Cu-Sn层后,再沉积Zn金属层,制备出Cu-Sn-Zn金属预制层。在不同的温度下进行低温退火后,以硫粉作为硫源高温硫化金属预制层,制备出晶体质量较好的Cu2ZnSnS4(CZTS)薄膜。通过X射线衍射仪(XRD)、扫描电镜(SEM)及能谱仪(EDS)对薄膜的晶体结构、表面形貌和薄膜组分进行分析表征,发现共沉积Cu-Sn层,再沉积Zn金属层得到的CZT预制层表面平整但晶粒尺寸较小,经过退火处理后晶粒尺寸得到改善,且硫化后所得到的CZTS薄膜不易从Mo衬底上脱落,粘附性较强。用其制备的CZTS薄膜太阳电池的开路电压Voc=569mV,短路电流密度Jsc=8.58mA/cm2,光电转换效率为1.40%。     

Reaction pathway for synthesis of Cu<Subscript>2</Subscript>ZnSn(S/Se)<Subscript>4</Subscript> via mechano-chemical route and annealing studies

Reaction pathway for the formation of kesterite Cu₂ZnSn(S/Se)₄ (CZTS/Se) from elemental precursors (Cu, Zn, Sn, S/Se) has been investigated experimentally and is being reported in the current paper. To identify the various stages of reaction pathway and to identify the formation and consumption of secondary phases, X-ray diffraction and Raman spectroscopy tools were employed. A series of experiments for different ballmilling durations (5, 10, 15, 20, 25 and 30 h) were performed and the presence of different phases was recorded for each experiment. In addition to XRD and Raman studies, phase formation has also been confirmed using detailed XPS, TEM and SEM–EDS analysis. In addition, the effect of annealing temperature on composition and band gap of the CZTS/Se material has been discussed. Optical band gap of various samples of CZTS was observed in the range of 1.40–1.60 eV and that of CZTSe was observed in the range of 1.08–1.18 eV. The relatively simple, low cost, easily scalable mechanical alloying process along with understanding of reaction pathway will provide a future scope for bulk production of CZTS/Se absorber material for thin film solar cells.     

Enhancement in photovoltaic performance of CZTS Thin-film solar cells through varying stacking order and sulfurization time

The CZTS samples were produced by a two-stage method, which includes deposition of Cu, Sn, Zn, and ZnS layers using magnetron sputtering to obtain CuSn/Zn/Cu and CuSn/ZnS/Cu stacks. The latter stage involves the sulfurization process of stacked films at 550 °C for varied sulfurization time (60, 90, 120, and 150 s) employing Rapid Thermal Processing (RTP) method to attain CZTS structure. The prepared CZTS thin films were analyzed utilizing several characterization methods. The energy-dispersive X-ray spectroscopy (EDX) measurements revealed that all sulfurized samples had Cu-poor and Zn-rich chemical composition. All samples showed that diffraction peaks belonged to pure kesterite CZTS phase subject to their XRD patterns. Besides, it was observed that the sulfurization time had a crucial effect on the crystal size of the samples. The Raman spectra of the samples verified the constitution of kesterite CZTS phase and it provides detection of some CTS-based secondary phases. The scanning electron microscopy (SEM) image of the films revealed that polycrystalline surface structures were observable in all the samples. However, plate-like surface features were observed in some samples that may refer to CTS-based secondary phases depending on chemical composition. From 1.40 to 1.48 eV optical band gap values were obtained from (αhν)² vs. photon energy (hν) plots. The Van der Pauw measurements exhibited that the CZTS samples produced employing CuSn/ZnS/Cu stack had lower resistivity (~?10^–3 Ω cm), higher carrier concentration values (~?10²¹ cm^?3), and higher charge mobility. The solar cells prepared using the most promising CZTS samples employing CuSn/Zn/Cu and CuSn/ZnS/Cu precursor films revealed 1.95% and 3.10% conversion efficiencies, respectively.

     

Fabrication of Cu2ZnSnS4 absorber layers with adjustable Zn/Sn and Cu/Zn+Sn ratios

In this work Cu₂ZnSnS₄ (CZTS) thin films were successfully prepared by sulfurization of spin coated CuO + ZnO precursor films under Sn and S ambience with different time. Precursor films were synthesized using air-stable inks consist of carboxylate-capped metal oxide nanoparticles. The composition, microstructure and properties of CZTS thin films prepared with different sulfurization time were investigated using inductively coupled plasma-mass spectrometry, X-ray diffraction, scanning electron microscopy, Raman spectroscopy and UV–vis–NIR spectroscopy. The inductively coupled plasma-mass spectrometry results show that mole ratios of Zn/Sn and Cu/(Zn + Sn) in the films can be adjusted by controlling sulfurization time. A composition of Cu/Zn + Sn = ~0.8, and Zn/Sn = ~1.2 can be reached after sulfurizating with proper time. The influence of element composition change was also studied in our work using X-ray diffraction and Raman scattering. Two laser sources of 325 and 514 nm were involved in the Raman scattering analyze in order to identify secondary phases such as ZnS and Cu_2?xS. The as-prepared CZTS films with a composition of Cu/Zn + Sn = ~0.8, and Zn/Sn = ~1.2 exhibit a direct optical band gap about 1.45 eV.     

Cu2ZnSnS4 films by paste coating and their optoelectronic properties

Cu₂ZnSnS₄ (CZTS) thin films were prepared by a paste coating method as the absorb layer of solar cells. This method is more eco-friendly using ethanol as solvent and more convenient than traditional sol–gel method. The effects of sulfurization temperature on properties of thin film were studied. The results of X-ray diffraction and Raman spectroscopy showed the formation of kesterite structure of CZTS films. The scanning electron microscopy images revealed that CZTS thin film obtained at 550 °C were compact and uniform. The optical band gap of the CZTS film was about 1.5 eV, and the CZTS film had an obvious optoelectronic response. Moreover, CZTS solar cell was prepared with a conversion efficiency of 0.47 %.     

Sulfurization time effects on the growth of Cu2ZnSnS4 thin films by solution method

Cu₂ZnSnS₄ (CZTS) films were obtained by sulfurizing (Cu, Sn) S/ZnS structured precursors prepared by a combination of the successive ionic layer absorption and reaction method and the chemical bath deposition method, respectively. The effect of sulfurization time on structure, composition and optical properties of these CZTS thin films was studied. The results of energy dispersive spectroscopy indicate that the annealed CZTS thin films are of Cu-poor and Zn-rich states. The X-ray diffraction studies reveal that Cu_2?x S phase exists in the annealed CZTS thin film prepared by sulfurization for 20 min, while the Raman spectroscopy analysis shows that there is a small Cu₂SnS₃ phase existing in those by sulfurization for 20 and 40 min. The band gap (E _g ) of the annealed CZTS thin films, which are determined by reflection spectroscopy, varies from 1.49 to 1.56 eV depending on sulfurization time. The best CZTS thin film is the one prepared by sulfurization for 80 min, exhibiting a single kesterite structure, dense morphology, ideal band gap (E _g  = 1.55 eV) and high optical absorption coefficient (>10⁴ cm^?1).     

Preparation of Cu2ZnSnS4 thin films by sulfurization of stacked metallic layers

Stacked precursors of Cu, Sn, and Zn were fabricated on glass/Mo substrates by electron beam evaporation. Six kinds of precursors with different stacking sequences were prepared by sequential evaporation of Cu, Sn, and Zn with substrate heating. The precursors were sulfurized at temperatures of 560 °C for 2 h in an atmosphere of N₂ + sulfur vapor to fabricate Cu₂ZnSnS₄ (CZTS) thin films for solar cells. The sulfurized films exhibited X-ray diffraction peaks attributable to CZTS. Solar cells using CZTS thin films prepared from six kinds of precursors were fabricated. As a result, the solar cell using a CZTS thin film produced by sulfurization of the Mo/Zn/Cu/Sn precursor exhibited an open-circuit voltage of 478 mV, a short-circuit current of 9.78 mA/cm², a fill factor of 0.38, and a conversion efficiency of 1.79%.     

Growth and properties of Cu<Subscript>2</Subscript>ZnSnS<Subscript>4</Subscript> thin films prepared by multiple metallic layer stacks as a function of sulfurization time

In this paper, we report the two stage growth of Cu₂ZnSnS₄ (CZTS) thin films as a function of sulfurization time. First, magnetron sputtered metallic precursors were deposited sequentially (Zn/Cu/Sn/Cu) over rotating glass substrates held at 230?°C. Later, the sputtered precursors were heat treated at 500?°C in the ambiance of sulfur for various time durations in the range, 10–120 min. The sulfur treated samples were examined using various analytical tools to understand the role of sulfurization time on the CZTS growth and properties. From composition and structural analysis, Zn/Cu/Sn/Cu precursors sulfurized for shorter duration (10 and 20 min) revealed severe deficiency of sulfur that resulted in several metallic, bi-metallic and metal sulfide phases. With the increase of sulfurization time to 30 min, sulfur incorporation was enhanced and reached stoichiometric ratio (~50% S) for CZTS growth, however, samples were poorly crystalline in nature and consisted of prominent Cu_2?xS phase as well. The Zn/Cu/Sn/Cu precursors sulfurized for 60 min exhibited prominent CZTS phase without Cu_2?xS phase. Further, rise in sulfurization time to 120 min enabled drastic improvement in crystallinity of CZTS phase. Raman mapping over 60 µm × 60 µm for these films confirmed the homogeneous phase growth of CZTS. XPS study revealed the oxidation states of Cu¹⁺, Zn²⁺, Sn⁴⁺ and S^2? in CZTS films. The optimized films showed high absorption coefficient of 10⁵ cm^?1 with an optical band gap of 1.51 eV. These films showed leaf like grain morphology with high mobility and low resistivity of 18.2 cm²/V-s and 0.7 Ω-cm, respectively.