利用溅射ITO层增强钙钛矿太阳电池的稳定性研究

为增强以银为背电极的正置结构有机-无机金属卤化物钙钛矿太阳电池（PSCs）的长期稳定性,研究利用射频磁控溅射技术在氧化钼层与银背电极之间沉积一层铟锡氧化物（ITO）来对PSCs进行内封装的技术。为防止ITO层溅射对下方已沉积的钙钛矿层和有机空穴传输层造成损伤,研究ITO层溅射功率和厚度对PSCs光伏性能的影响,获得优化的ITO层制备工艺,发现在ITO层溅射功率为30 W、厚度为40 nm时所制备的PSCs光伏性能最优。为进一步提升PSCs性能,对比溅射法和热蒸发法沉积银背电极对PSCs性能的影响,发现与蒸发法相比,采用溅射银背电极的PSCs光伏性能更佳,其光电转换效率可达到17.86%。PSCs光伏性能的长期稳定性测试和X射线衍射结果分析表明,溅射ITO阻隔层的插入可有效抑制钙钛矿层中的卤素离子与银背电极之间的扩散反应,在不降低PSCs效率的同时可显著改善PSCs稳定性,所制备的PSCs在干燥空气中存放4500h后仍能保持初始效率的95%。     

氧化钼在半透明双面钙钛矿太阳电池中的应用

研究双面钙钛矿太阳电池正极窗口叠层MoO_3/ITO(氧化钼/掺锡氧化铟),通过蒸镀法沉积制备具有不同厚度的氧化钼(MoO_3)缓冲层。结合PV Lighthouse模拟计算,系统分析MoO_3缓冲层对太阳电池光电性能的影响。得益于电子传输层的宽禁带和MoO_3/ITO的减反效果,当光从玻璃衬底(SnO_2电子传输层)一侧入射时电池的短路电流密度较高。实验表明当MoO_3缓冲层厚度在10～15 nm时,钙钛矿太阳电池填充因子和短路电流密度达到最佳值,此时电池光电转换效率最高,电池的双面率为69.5%。     

MoO3界面修饰提升刮涂钙钛矿太阳电池性能

在空穴传输层Spiro-OMeTAD和Ag电极之间引入三氧化钼(MoO₃)空穴修饰层,并研究其对空气中刮涂的钙钛矿太阳电池光伏性能的影响,结合导电性测试、稳态光致发光光谱和水接触角测试等探究其影响机制。实验和测试结果表明MoO₃可提升空穴传输能力和减小界面电阻,同时对下方的Spiro-OMeTAD及钙钛矿起到保护作用,可减缓空气中水氧侵蚀。基于MoO₃界面修饰层的在空气中刮涂制备的钙钛矿太阳电池光电转换效率由15.14%提升至18.30%,尤其是填充因子的平均值由60%提升至76%,电池稳定性得到改善,未封装电池在400 h后仍保持初始效率的90%。     

钙钛矿敏化太阳电池制备工艺的优化研究

近年来,有机金属卤化物钙钛矿太阳电池因制备条件温和、光吸收强、能耗低、光电转化效率高等优点成为备受瞩目的研究热点。本文采用一步法制备钙钛矿材料甲胺碘化铅（CH3NH3PbI3）,并以廉价的聚（3-己基噻吩） （P3HT）为空穴传输材料在大气环境下制备钙钛矿敏化太阳电池。其中,通过调控TiO2浆料与松油醇、乙基纤维素的配比,分别制备具有250 nm、600 nm和1 000 nm三种不同厚度的TiO2纳米颗粒多孔薄膜光阳极,并系统考察钙钛矿前驱体溶液旋涂量对敏化电极结构形貌及光吸收性能的影响。太阳电池光电特性测试结果表明：当TiO2多孔层厚度为600 nm、钙钛矿前驱体溶液的旋涂量为40 μl时,CH3NH3PbI3能够较为完全地覆盖在多孔TiO2的表面,且钙钛矿材料的晶粒尺寸合适,TiO2孔道结构未被堵塞,有利于空穴导体的填充以及空穴的转移与传输,优化后的太阳电池光电转化效率达到5.17%。     

有机太阳电池ITO电极质量衡量方法

通过测量不同光刻条件下制作的ITO极的方块电阻,提供了一种利用方块电阻测量值来衡量有机太阳电池ITO电极质量的方法.对于笔者所使用的ITO电极图案和ITO玻璃的规格,在指定点上测得方块电阻为7.0Ω/□时,电极质量较好.相比利用显微镜观察ITO电极质量的方法,该方法既简便又准确,可以提供一个对ITO电极质量的量化衡最标准.     

连续旋涂提高钙钛矿太阳电池开路电压的研究

在钙钛矿太阳电池的制作过程中,通过改善旋涂方法和条件,可大大提高钙钛矿吸收层的结晶性以及太阳电池的光电转换性能。与常规的一次性旋涂方法相比,采用连续二次旋涂方法制作的钙钛矿薄膜更加致密,结晶性明显提高。旋涂时前驱液和衬底的温度会影响钙钛矿层的晶体结构,温度为60℃时,钙钛矿的平均晶粒尺寸约为500 nm,且晶粒之间致密排列,导致光学带隙增加。采用连续二次旋涂方法,在加热温度为60℃时制作的钙钛矿太阳电池的光电转换效率达到14.7%,其中短路电流密度、开路电压和填充因子分别为18.9 m A/cm~2、1.13 V和69%。与常规钙钛矿太阳电池相比,开路电压提高约100 m V。依据暗态J-V测试结果,二次旋涂工艺条件下,该光伏器件的反向饱和电流密度约为10~(-5)m A/cm~2,比一次旋涂工艺降低3个数量级。     

高效硅基异质结太阳电池的ITO薄膜研究

研究室温下通过直流磁控溅射方法制备高性能非晶ITO薄膜的光电特性,并分析不同结晶度的ITO薄膜对硅基异质结太阳电池性能的影响。结果表明:非晶态的ITO薄膜具有高的载流子迁移率和高的光学透过率;当退火温度高于190℃时,随退火温度的上升,薄膜的结晶性逐渐增强,但其光学性能和电学性能都呈逐渐降低的趋势。通过优化退火温度可获得电阻率为4.83×10^-4Ω·cm、载流子迁移率高达35.3 cm²/(V·s)且长波段相对透过率大于90%的高性能非晶ITO薄膜。对比普通工艺制备的微晶ITO薄膜,在242.5 cm²的硅基异质结(SHJ)太阳电池上采用非晶ITO薄膜作透明导电膜,其短路电流密度提高0.32 mA/cm²,可提升电池的光电转换效率。     

ITO/Si异质结太阳电池

铟锡氧化物/硅太阳电池,简称ITO/Si太阳电池,其优点是结构简单,避免高温扩散工艺,不仅适用于单晶材料,更适用于多晶和非晶材料,有较好的短波响应,形成p-n结的ITO膜又可兼作减反射膜。ITO/Si太阳电池的制作,可以采用喷涂、真空蒸镀、溅射和化学气相沉积等方法。本文仅介绍真空蒸镀法制作ITO/Si太阳电池。     

HIT太阳电池中ITO薄膜的结构和光电性能

采用射频磁控溅射技术在不同射频功率下沉积了ITO薄膜,并将其应用于HIT太阳电池。分析了薄膜的结构、光电特性。结果表明,在120W时制备的薄膜很好地兼顾了电阻率和光透过率,其电阻率为3.48×10-4Ω.cm、在350~800 nm波段的平均光透过率为87.1%,将其应用于HIT太阳电池上,电池的转换效率可达13.38%。     

高效柔性钙钛矿太阳电池研究

对柔性钙钛矿太阳电池(FPSCs)成膜工艺进行研究,针对在柔性基底上沉积薄膜不均匀、较多缺陷、内部应力等问题,分析其形成原因和影响因素。选择PET/ITO作为柔性基底,SnO₂作为电子传输层,加入KCl进行调控,KCl的加入可增加电子传输层与柔性导电基底的亲和性,从而获得致密且缺陷较少的膜层。通过优选钙钛矿前驱体各组分配比,加入MACl作为添加剂调控结晶过程,并在钙钛矿表面设计PEAI钝化层钝化界面,获得高质量的钙钛矿结晶和致密表面,并使电池的柔韧性能得到提升。在适宜的环境下,制备认证效率达到23.14%的柔性钙钛矿太阳电池,其在弯折10000次后仍能保持80.48%的初始光电转换效率。     

ITO/metal/ITO multilayer structures based on Ag and Cu metal films for high-performance transparent electrodes

Transparent conductive indium tin oxide (ITO)/metal/ITO multilayer electrodes have been prepared by sputtering at room temperature. Ag and Cu thin films with thickness ranging from 5 to 35 nm have been used as intermediate metal layer, between ITO coatings of about 30 nm thickness. Evolution of the optical and electrical characteristics of the multilayers as a function of each metal film thickness has been analyzed. High-quality transparent electrodes have been obtained, with sheet resistance below 6 Ω/sq for Ag film thickness above 10 nm or Cu film thickness above 16 nm. These multilayers also showed high transmittance in the visible spectral range, above 90% by discounting the glass substrate, with a maximum that is located at lower wavelength for Ag-based electrodes than for the Cu-based ones. After heating at 350 °C in flowing nitrogen, some improvement in the optoelectronical characteristics of the multilayer electrodes has been achieved that is related to the structural improvement of the ITO components.     

Low resistance and highly transparent ITO–Ag–ITO multilayer electrode using surface plasmon resonance of Ag layer for bulk-heterojunction organic solar cells

We comprehensively investigated the electrical, optical, structural, mechanical, interfacial, and surface properties of ITO–Ag–ITO (IAI) multilayer electrodes grown on glass substrates by linear facing target sputtering (LFTS) for bulk-heterojunction organic solar cells (OSCs). Although the single ITO electrode with a thickness of 150 nm showed a fairly high sheet resistance of 34 Ω/square, the IAI multilayer electrode exhibited a very low sheet resistance of 4.4 Ω/square due to the low resistivity of the inserted Ag layer. Without using a substrate heating or post-annealing process, we were able to obtain an IAI multilayer electrode with a low sheet resistance, comparable to that of a crystalline ITO electrode, using the room-temperature LFTS process. In addition, the surface plasmon resonance (SPR) and antireflection of the optimized Ag layer significantly increased the optical transmittance of the IAI multilayer. It was found that the optimization of the thickness of the Ag layer is very important to obtain transparent IAI multilayer electrodes, because the SPR effect is critically affected by the Ag morphology. Moreover, the OSC fabricated on the optimized IAI electrode with an Ag thickness of 16 nm showed a higher power conversion efficiency (3.25%) compared to that prepared on the amorphous ITO electrode (2.35%), due to its low sheet resistance and high optical transmittance at 400–600 nm, which corresponds to the absorption wavelength of the organic active layer. This indicates that IAI multilayer electrodes grown by LFTS are promising transparent conducting electrodes for OSCs or flexible OSCs due to their very low resistivity and high optical transmittance.     

Nano-sized Ag-inserted amorphous ZnSnO3 multilayer electrodes for cost-efficient inverted organic solar cells

A sheet resistance- and optical transmittance-tunable amorphous ZnSnO₃ (ZTO) multilayer electrode created through the insertion of a nano-scale Ag layer is demonstrated as an indium-free transparent conducting electrode for cost-efficient inverted organic solar cells (IOSCs). Due to the antireflection effect, the ZTO/Ag/ZTO/glass exhibited a high transmittance of 86.29% in the absorption wavelength region of the organic active layer and a low resistivity of 3.24×10⁻⁵ Ω cm, even though the ZTO/Ag/ZTO electrode was prepared at room temperature. The metallic conductivity of the electrode indicates that its electrical conductivity is dominated by the nano-scale Ag metal layer. In addition, optimization and control of the thickness of the nano-scale Ag layer are important in obtaining highly transparent ZTO/Ag/ZTO electrodes, because antireflection is strongly influenced by Ag thickness. Moreover, IOSCs fabricated on optimized ZTO/Ag/ZTO electrodes with Ag thicknesses of 12 nm showed power conversion efficiencies (2.55%) comparable to that of an IOSC prepared on a crystalline ITO electrode (2.45%), due to the low sheet resistance and high optical transmittance in the range of 400-600 nm. The performances of ZTO/Ag/ZTO multilayer electrodes indicate that ZTO/Ag/ZTO multilayers are promising as indium-free, transparent electrode substitutes for conventional ITO electrodes in cost-efficient IOSCs.     

Effect of the Cu underlayer on the optoelectrical properties of ITO/Cu thin films

Sn doped indium oxide (ITO) single layer films and ITO/Copper (Cu) bi-layer films were prepared on polycarbonate substrates by DC and RF magnetron sputtering without intentional substrate heating. In order to consider the influence of the Cu underlayer on the optoelectrical properties and microstructures of the films, the thickness of the Cu bottom layer in the ITO/Cu films was varied from 5 to 20 nm.Conventional ITO films had a constant optical transmittance of 74% and an electrical resistivity of 3.1 × 10⁻³ Ω cm, while ITO/Cu films had different optoelectrical properties that were influenced by the thickness of the Cu bottom layer. The lowest electrical resistivity, 5.7 × 10⁻⁵ Ω cm, was obtained from ITO 80 nm/Cu 20 nm films and the highest optical transmittance of 72%, was obtained from the ITO 95 nm/Cu 5 nm films. From the figure of merit (_TC) which is defined by _TC = T¹⁰/R_s, where T is the optical transmittance at 550 nm and R_s is the sheet resistance, it can be concluded that the most effective Cu thickness in the ITO/Cu films on the optoelectrical properties was 5 nm.     

Optimum design and its experimental approach of a-Si/ /poly-Si tandem solar cell

A series of technical data on four-terminal a-Si/ /poly-Si stacked solar cells has been reported. The developed device has some unique significances such as high achievable efficiency, and low cost with almost no light induced degradation. It has been shown on a poly-Si bottom cell that an efficiency of 17.2% has been obtained by employing high conductivity with wide optical band-gap p-type μc-SiC as a window material and n-type μc-SiC as a back ohmic contact with BSF effects. On the optically transparent a-Si top cell, an optimum design has been experimentally made with the device structure of p μc-SiC/p a-SiC/i a-Si/n μc-Si/ITO, and an efficiency of 7.25% has been obtained with a 100 nm thick i-layer, while the best efficiency is 12.3% for p-i-n single-junction solar cell with 500 nm i-layer thickness deviced by Ag back-electrode. With the 100 nm thick ultrathin top cell, a total conversion efficiency as high as 21.0% has been achieved on a-Si/ /poly-Si four-terminal tandem solar cells.     

Fabrication and opto-electric properties of ITO/ZnO bilayer films on polyethersulfone substrates by ion beam-assisted evaporation

Transparent conducting oxides bilayer films stacked by one 130-nm-thick indium tin oxide (ITO) top layer and one 75-nm-thick zinc oxide (ZnO) buffer layer were grown onto polyethersulfone (PES) substrates by ion beam-assisted evaporation. The effects of ion energy and ZnO buffer layers on the structural and opto-electric properties of ITO films were initially investigated. The as-deposited ZnO buffer layers show wurtzite (0 0 2) preferred orientation on the PES substrates with ion beam assistance. The results of X-ray diffraction reveal a marked increase in the crystallinity of the ITO films which use ZnO as a buffer layer material. A drop of ∼60% in electrical resistivity of the ITO film on the PES can be achieved by using ZnO buffer layer. The transmittance of the ITO/ZnO bilayer was not deteriorated due to the insertion of ZnO layer. The lowest electrical resistivity of 6.552×10⁻⁴ Ω-cm associated with the transmittance of ∼80% at the wavelength of 550 nm can be obtained for the ITO film on the ZnO-coated PES at ion energy of 60 eV. The ITO films on the ZnO-buffered PES with moderate control of ion energy have a promising future for the application of the contact layers for flexible solar cells.     

Novel device structure for Cu(In,Ga)Se2 thin film solar cells using transparent conducting oxide back and front contacts

Cu(In_1−xGa_x)Se₂ (CIGS)-based thin film solar cells fabricated using transparent conducting oxide (TCO) front and back contacts were investigated. The cell performance of substrate-type CIGS devices using TCO back contacts was almost the same as that of conventional CIGS solar cells with metallic Mo back contacts when the CIGS deposition temperatures were below 500 °C for SnO₂:F and 520 °C for ITO. CIGS thin film solar cells fabricated with ITO back contacts had an efficiency of 15.2% without anti-reflection coatings. However, the cell performance deteriorated at deposition temperatures above 520 °C. This is attributed to the increased resistivity of the TCO’s due to the removal of fluorine from SnO₂ or undesirable formation of a Ga₂O₃ thin layer at the CIGS/ITO interface. The formation of Ga₂O₃ was eliminated by inserting an intermediate layer such as Mo between ITO and CIGS. Furthermore, bifacial CIGS thin film solar cells were demonstrated as being one of the applications of semi-transparent CIGS devices. The cell performance of bifacial devices was improved by controlling the thickness of the CIGS absorber layer. Superstrate-type CIGS thin film solar cells with an efficiency of 12.8% were fabricated using a ZnO:Al front contact. Key techniques include the use of a graded band gap Cu(In,Ga)₃Se₅ phase absorber layer and a ZnO buffer layer along with the inclusion of Na₂S during CIGS deposition.     

A highly efficient light-trapping structure for thin-film silicon solar cells

A highly efficient light-trapping structure, consisting of a diffractive grating, a distributed Bragg reflector (DBR) and a metal reflector was proposed. As an example, the proposed light-trapping structure with an indium tin oxide (ITO) diffraction grating, an a-Si:H/ITO DBR and an Ag reflector was optimized by the simulation via rigorous coupled-wave analysis (RCWA) for a 2.0-μm-thick c-Si solar cell with an optimized ITO front antireflection (AR) layer under the air mass 1.5 (AM1.5) solar illumination. The weighted absorptance under the AM1.5 solar spectrum (A_AM1.5) of the solar cell can reach to 69%, if the DBR is composed of 4 pairs of a-Si:H/ITOs. If the number of a-Si:H/ITO pairs is up to 8, a larger A_AM1.5 of 72% can be obtained. In contrast, if the Ag reflector is not adopted, the combination of the optimized ITO diffraction grating and the 8-pair a-Si:H/ITO DBR can only result in an A_AM1.5 of 68%. As the reference, A_AM1.5 = 31% for the solar cell only with the optimized ITO front AR layer. So, the proposed structure can make the sunlight highly trapped in the solar cell. The adoption of the metal reflector is helpful to obtain highly efficient light-trapping effect with less number of DBR pairs, which makes that such light-trapping structure can be fabricated easily.     

15.1% Highly efficient thin film CdS/CdTe solar cell

High-efficiency CdS/CdTe solar cells with thin CdS film have recently been developed. Semiconductive layers of CdS via the CVD method and of CdTe via the CSS method were deposited on an ITO/#7059 substrate. Cell performance depends primarily on the thickness of CdS film, and the conversion efficiency is highest for a CdS film thickness of around 60 nm. Since the CdS film thickness decreases by about 30% during deposition of the CdTe layer, a thickness of 95 nm is required to obtain a 60 nm-thick CdS film after deposition of a CdTe layer. By observing the CdS film during the CdTe deposition process, a decrease was detected before CdTe layer completely covers the surface of the CdS film. By optimizing the thickness of CdS film, an efficiency of 15.12% for the best cell under AM 1.5 verified at JQA was obtained. This fabrication process has good reproducibility; 92.5% of 1 cm² solar cells fabricated under the same conditions have efficiencies above 14%.     

MoOx/Ag/MoOx multilayers as hole transport transparent conductive electrodes for n-type crystalline silicon solar cells

Substitution of highly doped layers with conventional transparent conductive electrodes as carrier collecting and selective contacts in conventional crystalline silicon (c-Si) solar cell configurations is crucial in increasing affordability of solar cells by lowering material costs. In this study, oxide/metal/oxide (OMO) multilayers featuring molybdenum oxide (MoO_x) and silver (Ag) thin films are developed by thermal evaporation technique, as dopant-free hole transport transparent conductive electrodes (HTTCEs) for n-type c-Si solar cells. Semidopant-free asymmetric heterocontact (semi-DASH) solar cells on n-type c-Si utilizing OMO multilayers are fabricated. The effect of outer MoO_x layer thickness and Ag deposition rate on the photovoltaic characteristics of the fabricated semi-DASH solar cells are investigated. A comparison of front side pyramid textured and flat surface solar cells is performed to optimize the optical and electrical properties. Highest efficiency of 9.3% ± 0.2% is achieved in a pyramid textured semi-DASH c-Si solar cell with 15/10/30 nm of HTTCE structure.