铜铟镓硒薄膜太阳电池研究进展和挑战

铜铟镓硒(Cu（In,Ga）Se₂,CIGS)太阳电池产业化受到全世界广泛关注。作为高转换效率薄膜电池,其效率可与晶硅电池相比,目前最高效率达到23.35%。对于小面积实验室电池而言,研究重点是精确控制吸收层的化学计量比和效率;对于工业化生产而言,除化学计量比和效率外,成本、重现性、产出和工艺兼容性在商业化生产中至关重要。重点介绍了不同制备工艺、吸收层组分梯度调控、碱金属后沉积处理、宽带隙无镉缓冲层、透明导电层和柔性衬底等研究进展。从CIGS电池的效率来看,将实验室创纪录的高效电池技术转移到平均工业生产水平带来显而易见的挑战。     

HDI板跨层孔孔内无铜的失效机理探究

在5G通讯大背景下,对PCB提出了越来越高的布线和信号要求,跨层孔设计已广泛应用在Whitley平台的服务器板上。文章针对跨层孔孔内无铜问题进行分析,发现是沉铜生产过程中盲孔内溶液交换不良产生,通过加大流量与提高药水浓度可促进盲孔内外溶液交换,有效解决了此类问题。     

利用多光子电离显微术研究铜铟镓硒薄膜太阳电池的微纳米膜层结构

基于超短脉冲激光多光子电离显微成像原理,利 用平均功率50μW、脉冲重复频率1kHz的 50fs激光脉冲,对铜铟镓硒(CIGS)薄膜太阳电池进行深度扫描, 比较分析了单纯钠钙玻璃衬底、镀钼钠钙 玻璃和铜铟镓硒/钼膜层/钠钙玻璃三种不同结构样品飞秒激光电离辐射信号的差别。实验发 现,对应于不同膜 层材料的飞秒激光诱导的电离辐射信号强度明显不同,在钠钙玻璃中电离辐射信号的强度约 为空气本底的 20倍,在Mo背电极层信号强度约为钠钙玻璃衬底的50倍,而CIGS层则出现与其带隙相对应的吸收谷, 谷的强度与空气背景相同,利用多光子电离显微术对太阳电池进行逐点扫描可以对CIGS和Mo 背电极层 的成膜质量、吸收带隙和微纳结构进行精细研究。分析表明,超短脉冲多光子电离显微术对 不同物质边界处 的变化非常敏感,在具有多层结构的复杂器件的微观特性检测方面具有独特的优势。     

Cu(In,Ga)Se2太阳电池缓冲层ZnS薄膜性质及应用

在含有ZnSO4,SC(NH2)2,NH4OH的水溶液中采用CBD法沉积ZnS薄膜,XRF和热处理前后的XRD测试表明,ZnS沉积薄膜为立方相结构,薄膜含有非晶态的Zn(OH)2.光学透射谱测试表明,制备的薄膜透过率(λ＞500nm)约为90%,薄膜的禁带宽度约为3.51eV.ZnS薄膜沉积时间对Cu(In,Ga)Se2太阳电池影响显著,当薄膜沉积时间在25～35min时,电池的综合性能最好.对比了不同缓冲层的电池性能,采用CBD-CdS为缓冲层的电池转换效率、填充因子、开路电压稍高于CBD-ZnS为缓冲层的无镉电池,但无镉电池的短路电流密度高于前者,两者转换效率相差2%左右.ZnS可以作为CIGS电池的缓冲层,替代CdS,实现电池的无镉化.     

不同深宽比GaAs衬底的Al22O3/HfO2复合薄膜材料原子层沉积及能谱分析

利用热原子层沉积（Atomic Layer Deposition, ALD）技术在不同深宽比GaAs衬底上进行了Al2₂O₃/HfO₂复合薄膜的沉积。通过对其表面和能谱进行分析发现,沉积温度对复合薄膜的摩尔比具有较大的影响。随着深宽比的增大,其沉积表面和沟槽内会出现残留物;随着ALD沉积温度的上升,其沉积表面和沟槽内的残留物减少,摩尔比趋向均匀。当深宽比为2.2并利用150 ℃的低沉积温度时,表面及底面基本无残留物。但当深宽比为4.25时,150 ℃沉积明显有大量残留物。只有当温度升高到300 ℃时,表面和沟槽里复合薄膜的残留物才被明显消除。ALD技术可以实现各种器件结构的全方位钝化,这是其他化学气相沉积法无法比拟的。     

Determination of activation barriers for the diffusion of sodium through CIGS thin‐film solar cells

We have determined the activation energies of sodium diffusion from the soda‐lime glass substrate through the Mo back‐contact layer, as well as through copper indium gallium diselenide (CIGS) deposited on the Mo back‐contact layer of CIGS thin‐film solar cells. The activation energies were determined by X‐ray photoelectron spectroscopy (XPS) to measure surface sodium concentrations before and after thermally induced diffusion. The activation energies were found to be similar for the diffusion of Na through the Mo/glass and CIGS/Mo/glass thin films, approximately 8·6 and 9·6 kcal/mol, respectively. Furthermore, the sodium diffusion was found to occur by annealing in an environment of 1·0×10⁻⁵ Torr of air, oxygen, or water vapor, but not in vacuum of less than 1×10⁻⁸ Torr. In addition, the diffusion of Na was found to occur faster in the presence of oxygen than in water under identical annealing conditions. Copyright © 2003 John Wiley & Sons, Ltd.     

Record 1.0 V open‐circuit voltage in wide band gap chalcopyrite solar cells

Tandem solar cell structures require a high‐performance wide band gap absorber as top cell. A possible candidate is CuGaSe₂, with a fundamental band gap of 1.7 eV. However, a significant open‐circuit voltage deficit is often reported for wide band gap chalcopyrite solar cells like CuGaSe₂. In this paper, we show that the open‐circuit voltage can be drastically improved in wide band gap p‐Cu(In,Ga)Se₂ and p‐CuGaSe₂ devices by improving the conduction band alignment to the n‐type buffer layer. This is accomplished by using Zn_1−x Sn_x O_y , grown by atomic layer deposition, as a buffer layer. In this case, the conduction band level can be adapted to an almost perfect fit to the wide band gap Cu(In,Ga)Se₂ and CuGaSe₂ materials. With an improved buffer band alignment for CuGaSe₂ absorbers, evaporated in a 3‐stage type process, we show devices exhibiting open‐circuit voltages up to 1017 mV, and efficiencies up to 11.9%. This is to the best of our knowledge the highest reported open‐circuit voltage and efficiency for a CuGaSe₂ device. Temperature‐dependent current‐voltage measurements show that the high open‐circuit voltage is explained by reduced interface recombination, which makes it possible to separate the influence of absorber quality from interface recombination in future studies.     

CIGS薄膜太阳能电池缓冲层CdS薄膜的制备研究

目前CdS材料的制备方法有很多种,但是最常用的是化学水浴法。本文研究了浓度、反应溶液pH值、温度、沉积时间对CdS缓冲层薄膜的影响,对CIGS薄膜太阳能电池缓冲层CdS薄膜的制备方法进行了论述。     

Designing novel thin film polycrystalline solar cells for high efficiency: sandwich CIGS and heterojunction perovskite

Heterojunction and sandwich architectures are two new-type structures with great potential for solar cells. Specifically, the heterojunction structure possesses the advantages of efficient charge separation but suffers from band offset and large interface recombination; the sandwich configuration is favorable for transferring carriers but requires complex fabrication process. Here, we have designed two thin-film polycrystalline solar cells with novel structures:sandwich CIGS and heterojunction perovskite, referring to the advantages of the architectures of sandwich perovskite (standard) and heterojunction CIGS (standard) solar cells, respectively. A reliable simulation software wxAMPS is used to investigate their inherent characteristics with variation of the thickness and doping density of absorber layer. The results reveal that sandwich CIGS solar cell is able to exhibit an optimized efficiency of 20.7%, which is much higher than the standard heterojunction CIGS structure (18.48%). The heterojunction perovskite solar cell can be more efficient employing thick and doped perovskite films (16.9%) than these typically utilizing thin and weak-doping/intrinsic perovskite films (9.6%). This concept of structure modulation proves to be useful and can be applicable for other solar cells.     

有机／无机光电探测器的AFM和XPS分析

采用真空蒸发沉积，在室温下制备了PTCDA／p—Si有机／无机异质结样品。对其表面用原子力显微镜(AFM)研究表明，PTCDA薄膜具有岛状形态结构。经X光电子能谱(XPS)分析表明，在PTCDA分子中，C原子有两种束缚能态，其结合能力分别为285．3eV和288．7eV；O原子与C原子相邻，一些O原子通过双键与C原子相结合，另外的O原子则通过单键与2个C原子相结合。经Ar^ 束溅射研究界面电子状态表明，随溅射时间增加，C1s和O1s峰逐渐减弱，而Si 2p和Si 2s峰渐渐增强。C1s和Si 2p谱峰随着溅射时间的增加而逐渐向低束缚能力方向移动。由于荷电效应和碳硅氧烷(C—Si—O)及SiO2的存在，Ols谱峰随溅射时间的增加先向高束缚能方向移动，然后向低束缚能方向移动。     

Atomic layer deposition of ZnO electron transporting layers directly onto the active layer of organic solar cells

Interlayers in organic solar cells (OSCs) are used to reduce energy barriers for charge injection/extraction, act as optical spacers, introduce carrier selectivity and increase organic/contact compatibility. To date, the most widely used inorganic interlayers are metal oxides such as TiO₂ and ZnO. However, these materials require harsh deposition conditions that could damage the organic active layers, and hence are generally used in inverted devices. Here we show, for the first time, that judicious selection of materials and processing conditions allow the use of an atomic layer deposition (ALD) system to deposit thin conformal ZnO interlayers on bulk heterojunctions (BHJs). ALD-ZnO interlayers were utilized as electron transporting layers (ETLs) in OSCs and compared to similar devices with solution deposited ZnO nanoparticle (np) ETLs. OSCs with ALD-ZnO ETLs exhibited higher photocurrent densities, J_sc, but lower open circuit voltages, V_oc. The low V_oc is associated with the presence of pinholes and an offset between the ALD-ZnO and PC₇₀BM electron conducting states. This offset results from traps and acceptor sites generated during the low temperature ALD process. To recover the V_oc we introduced a fluorinated phosphonic acid (PA) additive to the blend. We suggest that the additive migrates to the film surface, interacts with the ZnO to produce a denser layer and to passivate traps, effectively improving the device shunt resistance and energy level alignment and increasing V_oc. Overall, the devices with PA and ALD-ZnO ETLs possess significantly higher power conversion efficiencies (PCEs) than those with np-ZnO ETLs. For example, the champion ALD-ZnO device PCE is 3.5%, while that with np-ZnO is 2.75%.     

CIGS薄膜太阳能电池结构分析

阐述了影响铜铟镓硒(CIGS)薄膜太阳能电池性能和效率的技术因素,包括CIGS半导体材料的晶体结构、电池的结构组成、衬底材料的选择以及CIGS薄膜的Na掺杂等。分析了多元共蒸发法、硒化法沉积CIGS吸收层以及化学水浴法沉积Cd S缓冲层的具体工艺和特征,介绍了柔性CIGS薄膜太阳能电池的卷对卷技术,最后就CIGS薄膜太阳能电池的研发与商业化生产中遇到的挑战及解决方法进行了分析与归纳。     

Co‐optimization of SnS absorber and Zn(O,S) buffer materials for improved solar cells

Thin‐film solar cells consisting of earth‐abundant and non‐toxic materials were made from pulsed chemical vapor deposition (pulsed‐CVD) of SnS as the p‐type absorber layer and atomic layer deposition (ALD) of Zn(O,S) as the n‐type buffer layer. The effects of deposition temperature and annealing conditions of the SnS absorber layer were studied for solar cells with a structure of Mo/SnS/Zn(O,S)/ZnO/ITO. Solar cells were further optimized by varying the stoichiometry of Zn(O,S) and the annealing conditions of SnS. Post‐deposition annealing in pure hydrogen sulfide improved crystallinity and increased the carrier mobility by one order of magnitude, and a power conversion efficiency up to 2.9% was achieved. Copyright © 2014 John Wiley & Sons, Ltd.     

Theoretical simulation of performances in CIGS thin-film solar cells with cadmium-free buffer layer

Copper indium gallium selenium (CIGS) thin film solar cells have become one of the hottest topics in solar energy due to their high photoelectric transformation efficiency. To real applications, CIGS thin film is covered by the buffer layer and absorption layer. Traditionally, cadmium sulfide (CdS) is inserted into the middle of the window layer (ZnO) and absorption layer (CIGS) as a buffer layer. However, the application of the GIGS/CdS thin film solar cells has been limited because of the environmental pollution resulting from the toxic cadmium atom. Although zinc sulfide (ZnS) has been proposed to be one of the candidates, the performance of such battery cells has not been investigated. Here, in this paper, we systematically study the possibility of using zinc sulfide (ZnS) as a buffer layer. By including the effects of thickness, concentration of a buffer layer, intrinsic layer and the absorbing layer, we find that photoelectric transformation efficiency of ZnO/ZnS(n)/CIGS(i)/CIGS(p) solar cell is about 17.22%, which is qualified as a commercial solar cell. Moreover, we also find that the open-circuit voltage is~0.60 V, the short-circuit current is~36.99 mA/cm² and the filled factor is~77.44%. Therefore, our results suggest that zinc sulfide may be the potential candidate of CdS as a buffer layer.     

Enhanced photovoltaic performances of the dye-sensitized solar cell by utilizing rare-earth modified tin oxide compact layer

Multifunctional and ultrathin tin oxide (SnO₂) compact layer is modified by europium ion doped ytterbium fluoride (YbF₃:Eu³⁺), which is first designed and fabricated by a facile spin-coating method for the dye-sensitized solar cell (DSSC). The device with SnO₂/YbF₃:Eu³⁺ compact layer exhibits enhanced long-term stability and photoelectric conversion efficiency (PCE) compared to those of the device without compact layer. The enhanced long-term stability is due to the SnO₂/YbF₃:Eu³⁺ compact layer can transform ultraviolet (UV) light into visible light to mitigate dye degradation. The enhanced PCE is associated with the reduced recombination rate of electrons, the enhanced short-wavelength light response, and the high transparency of the compact layer. Moreover, the novel strategy of preparation SnO₂/YbF₃:Eu³⁺ compact layer is an universal method to adjust rare-earth species to achieve up- or down-conversion functions, and the multifunctional compact layer can be widely applied in the photovoltaic device.