高效钙钛矿太阳电池及其叠层电池研究进展

钙钛矿太阳电池及其叠层电池发展迅速,成为当前光伏领域的研究热点.有机无机卤化钙钛矿材料具有吸收系数高、带隙可调、制备工艺简单等优点,其单结太阳电池实验室效率从2009年的3.8％迅速提升到25.2％,两端钙钛矿/硅叠层太阳电池效率达到29.15％.钙钛矿太阳电池种类丰富,依据器件结构主要分为介孔型钙钛矿太阳电池和平面型(nip结构和pin结构)钙钛矿太阳电池.大量研究工作通过钝化工程、添加剂工程、能级匹配工程、组分工程等先进技术获得高质量的钙钛矿吸收层和光电性能好、低成本、无污染的电荷传输层,提升电荷提取效率,使得每种器件结构均能实现22％以上的超高效率.但常规钙钛矿材料光、湿、热稳定性差,部分研究通过改善吸收层的成分,研发出准二维钙钛矿太阳电池与全无机钙钛矿太阳电池,更加贴合实际应用.考虑到不同的应用场景,钙钛矿太阳电池又进一步分化出柔性钙钛矿太阳电池与半透明钙钛矿太阳电池,透明导电电极的研发成为该领域的重要突破方向.基于钙钛矿的叠层电池中,高效钙钛矿/硅叠层电池是研究重点,通过优化陷光策略和添加剂工程等方法降低光学损失与电学损失,能够在材料成本增长不大的情况下显著提升电池效率,极具市场竞争力.本文主要阐述了钙钛矿太阳电池及其叠层电池的发展历史、器件种类和结构、功能层材料特性、性能优化策略,并对其面临的挑战以及发展趋势进行了总结与展望.     

全钙钛矿叠层太阳能电池的发展与展望（英文）

目前,进一步提高太阳能电池的光电转换效率,降低其度电成本,是实现“双碳”目标的必行之路.全钙钛矿叠层太阳能电池兼备光电转换效率高和成本低廉的优势,近几年取得了巨大的发展,在国际上备受关注,是一种新兴的光伏技术.在展现出巨大潜力的同时,全钙钛矿叠层太阳能电池也面临着多方面的挑战.本文综述了近年来全钙钛矿叠层太阳能电池在宽带隙子电池、窄带隙子电池和隧穿结方面的研究进展,展望了全钙钛矿叠层太阳能电池在效率提升、稳定性改善以及大面积制备等方面的未来发展方向.     

钙钛矿叠层太阳电池结构与性能优化:模型预测和实验研究

随着光电性质优越的有机-无机金属卤化物钙钛矿材料的快速发展,钙钛矿太阳电池受到了众多研究者的关注,以钙钛矿太阳电池作为顶层电池的叠层电池也受到了研究者的重视。经研究发现这种叠层电池的光电转换效率理论值高于35%,并且制作成本低,生产工艺简单,从而有可能孕育出光伏器件发展的新突破。主要介绍钙钛矿叠层太阳电池的结构、工艺制备,及其性能、效率等方面的最新进展。     

纳米金属氧化物在钙钛矿电池中的应用研究进展

近几年来, 钙钛矿电池发展迅速, 其单电池效率从最初的3.8%迅速提升至目前20.1%, 接近硅基太阳能电池的光电转换效率。TiO₂、ZnO、Al₂O₃等诸多无机纳米金属氧化物材料作为重要的载流子输运材料与钙钛矿生长骨架也被广泛地应用于钙钛矿电池。依据钙钛矿电池功能结构的差异, 本文分别介绍了此类材料作为钙钛矿电池中的致密层及介孔层的制备方法, 并在此基础上介绍了基于表面修饰、掺杂、复合等氧化物的改性手段调节材料理化性能与氧化物/钙钛矿界面特性, 进而改进钙钛矿电池性能的方法。并阐述了进一步提高钙钛矿电池光电转换效率需要关注的重点问题及展望。     

基于能带工程制备氧化镍基底的高效锡-铅共混钙钛矿太阳能电池

钙钛矿叠层太阳能电池因为具有超过肖克利-奎伊瑟效率极限的潜力而备受关注.窄带隙锡-铅(Sn-Pb)共混钙钛矿太阳能电池(PSCs)在钙钛矿叠层太阳能电池的构建中起着关键作用.制备稳定性好、可低温处理的空穴输送层是构建高效Sn-Pb钙钛矿太阳能电池和钙钛矿叠层太阳能电池的关键.在此,我们开发了一种室温处理的纳米晶体氧化镍...     

倒置结构全无机钙钛矿太阳能电池的界面层研究进展

铯基无机钙钛矿(CsPbX3)因其耐热性好、低成本和带隙可调等优点,近年来备受关注,并广泛用于制备新型薄膜太阳能电池。目前,虽然具有倒置结构的无机钙钛矿太阳能电池(PSC)更稳定且有望应用于构筑叠层电池的顶电池,其性能仍落后于正置结构的电池。因此,倒置电池的结构,特别是其界面层亟待进一步优化。近年来,研究者们设计和开发了一系列有机、无机界面层(包括空穴传输层和电子传输层),尝试优化基于无机钙钛矿的倒置电池。本综述针对这一现状,从材料和制备工艺的角度出发,综述了基于有机、无机材料体系的多种界面层的制备和应用进展,总结各类界面层材料的特点,讨论目前界面层的瓶颈问题和潜在的解决方案。     

CIGS叠层太阳能电池的中间层及稳定性的研究进展

叠层太阳能电池的问世开创了廉价、大面积、高效率太阳能电池制造与应用的新时代,当前研究最深入、应用最广泛的叠层电池主要有非晶硅/微晶硅(α-Si∶H/mc-Si∶H)的硅基叠层电池以及GaInP/GaAs为代表的Ⅲ-Ⅴ族化合物叠层电池,但是这两类叠层电池在长期光照下性能会发生衰退,影响电池的实际应用。因此人们为制造高稳定性和良好匹配度的叠层电池进行了不懈的努力,包括改进电池制造工艺和开发新材料体系的叠层电池等。铜铟镓硒(CIGS)是一种光吸收系数很高的材料且具有优异的光电性能,但CIGS叠层太阳能电池在光电转换过程中的衰减特别快,稳定性较差,远远达不到其理论效率;另外,CIGS硒化物的黄铜矿结构难以控制,导致其电学性能较差。将CIGS与Si电池叠加起来形成叠层电池,两者性能互补,既可提高CIGS材料的电导率,又可以拓宽Si电池的太阳光吸收波长范围。本文归纳了CIGS叠层太阳能电池器件的研究进展,并总结了各种叠层电池的中间结合层AZO(ZnO∶Al)、FTO(SnO_2∶F)、ITO(In_2O_3∶Sn)等的结构以及光电性能等方面的特点,从中间层、结构以及温度控制等方面论述了影响CIGS叠层太阳能电池稳定性的因素,分析了CIGS叠层太阳能电池面临的问题并展望了其前景,以期为制备稳定和高效率的新型CIGS叠层太阳能电池提供参考。     

非晶硅/非晶硅锗叠层电池器件结构优化与制备工艺研究

非晶硅/非晶硅锗叠层电池制备中非晶硅锗子电池本征层采用"喇叭口"结构。通过优化各层掺杂浓度,实现叠层电池光学带隙从1.95~1.5 eV之间的梯次平滑过渡(其中P层窗口层带隙1.95 eV,a-Si∶H1.7eV,a-SiGe∶H1.5eV)。探讨了NP隧穿结对叠层电池开路电压(Voc)和填充因子(FF)的影响,制备出FF为0.739的a-Si∶H/a-Si Ge∶H叠层电池。调整叠层电池中子电池本征层厚度,制备出效率为9.06%的a-Si∶H/a-SiGe∶H叠层电池(未加减反射层)。     

隧穿结对具有中间层的非晶硅/微晶硅叠层电池的影响

为了改善非晶硅/微晶硅叠层电池的载流子输运效果,将隧穿结引入到具有中间层结构的叠层电池中,研究了隧穿结的结构、掺杂浓度、厚度等条件对叠层电池性能的影响.实验结果表明,叠层电池中引入隧穿结构成“隧穿结-中间层”结构,可以进一步改善电池性能,经过结构和参数优化的隧穿结可以提高子电池的电流密度匹配度,提升叠层电池转换效率.加...     

半透明钙钛矿及叠层太阳电池中的透明电极研究综述

钙钛矿太阳电池由于具有独特的光电性能及制造工艺简单、低成本等特点而引起人们极大的关注。在钙钛矿太阳电池出现后的短短几年之内,其效率取得了突飞猛进的发展。在这个过程中,半透明钙钛矿太阳电池由于应用潜力巨大也受到越来越多的关注。特别是其与传统的硅电池或者铜铟镓硒电池组成的叠层太阳电池,由于其能够更加合理地利用太阳光谱而被认为是提升太阳电池光电转换效率的一条有效途径。到目前为止,半透明钙钛矿太阳电池的最高效率已达17.9%,叠层太阳电池的最高效率已达25.5%。顶部透明电极是半透明钙钛矿及叠层太阳电池的关键研究内容之一。对半透明钙钛矿及叠层太阳电池来说,理想的顶部透明电极应具有高透过率、低电阻、良好的化学稳定性以及能够在低温下制备等特点。截至目前,多种透明电极已经被应用于半透明钙钛矿及叠层太阳电池中,包括银纳米线、碳纳米管、超薄金属、石墨烯、导电聚合物以及透明导电氧化物等。银纳米线透明电极的光电性能良好,但稳定性较差,易与钙钛矿中的卤离子反应导致器件恶化,且在空气中易被氧化和腐蚀。超薄金属电极往往不能同时具有较高的导电性和光学透过率,需要引入合适的缓冲层来促使其均匀生长,但同样存在稳定性较差的问题。碳基透明电极的稳定性很强,但是其光电性能有待提高。透明导电氧化物具有良好的光电性能和稳定性,但往往采用溅射的方式制备,在溅射的过程中容易损伤钙钛矿活性层,需要引入合适的缓冲层。本文归纳了应用于半透明钙钛矿及叠层太阳电池中的透明电极的研究进展,分别对透明电极的种类、光电性能、制备工艺进行了系统的介绍,对比了各种透明电极光电性能及制备工艺的优缺点,分析了它们在研究中面临的问题并展望了其发展前景,以期为应用于半透明钙钛矿及叠层太阳电池的透明电极研究提供有益的参考。     

Single-graded CIGS with narrow bandgap for tandem solar cells

Multi-junction solar cells show the highest photovoltaic energy conversion efficiencies, but the current technologies based on wafers and epitaxial growth of multiple layers are very costly. Therefore, there is a high interest in realizing multi-junction tandem devices based on cost-effective thin film technologies. While the efficiency of such devices has been limited so far because of the rather low efficiency of semitransparent wide bandgap top cells, the recent rise of wide bandgap perovskite solar cells has inspired the development of new thin film tandem solar devices. In order to realize monolithic, and therefore current-matched thin film tandem solar cells, a bottom cell with narrow bandgap (~1 eV) and high efficiency is necessary. In this work, we present Cu(In,Ga)Se₂ with a bandgap of 1.00 eV and a maximum power conversion efficiency of 16.1%. This is achieved by implementing a gallium grading towards the back contact into a CuInSe₂ base material. We show that this modification significantly improves the open circuit voltage but does not reduce the spectral response range of these devices. Therefore, efficient cells with narrow bandgap absorbers are obtained, yielding the high current density necessary for thin film multi-junction solar cells.     

Highly Efficient Perovskite–Perovskite Tandem Solar Cells Reaching 80% of the Theoretical Limit in Photovoltage

Organic–inorganic hybrid perovskite multijunction solar cells have immense potential to realize power conversion efficiencies (PCEs) beyond the Shockley–Queisser limit of single‐junction solar cells; however, they are limited by large nonideal photovoltage loss (V _oc,loss) in small‐ and large‐bandgap subcells. Here, an integrated approach is utilized to improve the V _oc of subcells with optimized bandgaps and fabricate perovskite–perovskite tandem solar cells with small V _oc,loss. A fullerene variant, Indene‐C₆₀ bis‐adduct, is used to achieve optimized interfacial contact in a small‐bandgap (≈1.2 eV) subcell, which facilitates higher quasi‐Fermi level splitting, reduces nonradiative recombination, alleviates hysteresis instabilities, and improves V _oc to 0.84 V. Compositional engineering of large‐bandgap (≈1.8 eV) perovskite is employed to realize a subcell with a transparent top electrode and photostabilized V _oc of 1.22 V. The resultant monolithic perovskite–perovskite tandem solar cell shows a high V _oc of 1.98 V (approaching 80% of the theoretical limit) and a stabilized PCE of 18.5%. The significantly minimized nonideal V _oc,loss is better than state‐of‐the‐art silicon–perovskite tandem solar cells, which highlights the prospects of using perovskite–perovskite tandems for solar‐energy generation. It also unlocks opportunities for solar water splitting using hybrid perovskites with solar‐to‐hydrogen efficiencies beyond 15%.     

Amide‐Catalyzed Phase‐Selective Crystallization Reduces Defect Density in Wide‐Bandgap Perovskites

Wide‐bandgap (WBG) formamidinium–cesium (FA‐Cs) lead iodide–bromide mixed perovskites are promising materials for front cells well‐matched with crystalline silicon to form tandem solar cells. They offer avenues to augment the performance of widely deployed commercial solar cells. However, phase instability, high open‐circuit voltage (V_oc) deficit, and large hysteresis limit this otherwise promising technology. Here, by controlling the crystallization of FA‐Cs WBG perovskite with the aid of a formamide cosolvent, light‐induced phase segregation and hysteresis in perovskite solar cells are suppressed. The highly polar solvent additive formamide induces direct formation of the black perovskite phase, bypassing the yellow phases, thereby reducing the density of defects in films. As a result, the optimized WBG perovskite solar cells (PSCs) (E_g ≈ 1.75 eV) exhibit a high V_oc of 1.23 V, reduced hysteresis, and a power conversion efficiency (PCE) of 17.8%. A PCE of 15.2% on 1.1 cm² solar cells, the highest among the reported efficiencies for large‐area PSCs having this bandgap is also demonstrated. These perovskites show excellent phase stability and thermal stability, as well as long‐term air stability. They maintain ≈95% of their initial PCE after 1300 h of storage in dry air without encapsulation.     

A Semitransparent Inorganic Perovskite Film for Overcoming Ultraviolet Light Instability of Organic Solar Cells and Achieving 14.03% Efficiency

Organic solar cells (OSCs) can be unstable under ultraviolet (UV) irradiation. To address this issue and enhance the power conversion efficiency (PCE), an inorganic‐perovskite/organic four‐terminal tandem solar cell (TSC) based on a semitransparent inorganic CsPbBr₃ perovskite solar cell (pero‐SC) as the top cell and an OSC as bottom cell is constructed. The high‐quality CsPbBr₃ photoactive layer of the planar pero‐SC is prepared with a dual‐source vacuum coevaporation method, using stoichiometric precursors of CsBr and PbBr₂ with a low evaporation rate. The resultant opaque planar pero‐SC exhibits an ultrahigh open‐circuit voltage of 1.44 V and the highest reported PCE of 7.78% for a CsPbBr₃‐based planar pero‐SC. Importantly, the devices show no degradation after 120 h UV light illumination. The related semitransparent pero‐SC can almost completely filter UV light and well maintain photovoltaic performance; it additionally shows an extremely high average visible transmittance. When it is used to construct a TSC, the top pero‐SC acting as a UV filter can utilize UV light for photoelectric conversion, avoiding the instability problem of UV light on the bottom OSC that can meet the industrial standards of UV‐light stability for solar cells, and leading to the highest reported PCE of 14.03% for the inorganic‐perovskite/organic TSC.     

Metal halide perovskite: a game-changer for photovoltaics and solar devices via a tandem design

Multi-junction tandem design has been proven to be an effective means to further improve the efficiency of solar cells. However, its share in the photovoltaics market at present is tiny, since the most efficient tandem device comprises III-V semiconductors, which entail the use of expensive fabrication processes. The advent of perovskite solar cells, which have revitalized the PV field with their unprecedented pace of development, promises to address this bottleneck. Perovskite materials could not only serve as the top subcell absorber for commercial solar cells including Si and copper indium gallium selenide, but could work efficiently as bottom subcells owing to highly tuneable bandgaps which extend down to the range of ~1.2 to 1.5 eV. The highest-efficiency perovskite tandem to date was achieved by pairing a perovskite top cell with a Si bottom cell in a four-terminal configuration, yielding 26.4%. This review gives an overview of recent progress on the main tandem structures, and describes the detailed design improvements that have resulted in new record efficiencies. Ultimately, commercialization of these tandem solar cells relies on the scalability of perovskite technology. We, therefore, highlight the development of large-scale tandems and approaches to produce perovskite modules. We also point out the critical aspects that will require further effort and provide guidelines for future developments. The potential obstacles that will hamper the commercialization of perovskite tandems, if not adequately addressed, namely device stability and toxicity, are then critically examined. Finally, the substantial opportunities that perovskite materials open up for other solar devices with a tandem configuration are mentioned, which are attracting increasing attention.     

Stable and High-Efficiency Methylammonium-Free Perovskite Solar Cells

Organic–inorganic metal halide perovskite solar cells (PSCs) have achieved certified power conversion efficiency (PCE) of 25.2% with complex compositional and bandgap engineering. However, the thermal instability of methylammonium (MA) cation can cause the degradation of the perovskite film, remaining a risk for the long-term stability of the devices. Herein, a unique method is demonstrated to fabricate highly phase-stable perovskite film without MA by introducing cesium chloride (CsCl) in the double cation (Cs, formamidinium) perovskite precursor. Moreover, due to the suboptimal bandgap of bromide (Br⁻), the amount of Br⁻ is regulated, leading to high power conversion efficiency. As a result, MA-free perovskite solar cells achieve remarkable long-term stability and a PCE of 20.50%, which is one of the best results for MA-free PSCs. Moreover, the unencapsulated device retains about 80% of the original efficiencies after a 1000 h aging study. These results provide a feasible approach to enhance solar cell stability and performance simultaneously, paving the way for commercializing PSCs.     

High efficiency a-Si:H/a-Si:H solar cell with a tunnel recombination junction and a n-type μc-Si:H layer

In this paper, a-Si:H/a-Si:H tandem solar cells have been fabricated using a plasma enhanced chemical vapor deposition. The solar cell has a structure of glass/textured-SnO₂/p-a-SiC:H/i-a-Si:H/n-μc-Si:H/p-μc-Si:H/p-a-SiC:H/i-a-Si:H/n-μc-Si:H/gallium-doped zinc oxide/Ag. Higher efficiency in a-Si:H/a-Si:H tandem solar cells can be achieved by use of a good tunnel recombination junction (TRJ) and current matching. Accordingly, solar cells with a n-μc-Si:H/p-μc-Si:H TRJ are investigated. This paper studies the influence of the thickness of the top intrinsic amorphous silicon (i-a-Si:H) layer with regard to short circuit current density and current matching between the top and the bottom cells. Experimental results with lab-fabricated samples show that the optimal thickness of the i-a-Si:H layer in the top and bottom cells is 60 and 250 nm, respectively. An initial conversion efficiency of 10.29% is achieved for the optimized a-Si:H/a-Si:H tandem solar cell. Light-induced degradation of the solar cells is about 17%.     

Novel Types of Dye-Sensitized and Perovskite-Based Tandem Solar Cells with a Common Counter Electrode

Novel types of tandem solar cells (TSC) based on dye-sensitized (DSC) and perovskite (PSC) solar cells including DSC/DSC and DSC/PSC configurations with a common counter electrode were fabricated and investigated. The measurements of PV parameters for tandem solar cells under AM1.5 light intensity conditions have shown that the highest power conversion efficiency (PCE) of 14.5% was obtained for the DSC/DSC tandem configuration. At the same time, investigations of DSC/PSC tandem solar cells demonstrated the prospective benefits of this tandem system for obtaining high PCE values.     

Highly Efficient Semitransparent Solar Cells with Selective Absorption and Tandem Architecture

Semitransparent (ST) photovoltaics (PVs) with selective absorption in the UV or/and near‐infrared (NIR) range(s) and reduced energy losses, are critical for high‐efficiency solar‐window applications. Here, a high‐performance tandem ST‐PV with selected absorption in the desirable regions of the solar spectrum is demonstrated. An ultralarge‐bandgap perovskite film (FAPbBr_2.43Cl_0.57, E_g ≈ 2.36 eV) is first developed to fulfil efficient selective absorption in the UV region. After optimization, the corresponding ST single junction (SJ) PV exhibits an averaged transmittance (AVT) of ≈68% and an efficiency of ≈7.5%. By sequentially reducing the visible absorbing component in a low‐bandgap organic bulk‐heterojunction layer, an ST‐PV with selective absorption in the NIR is achieved with a power conversion efficiency (PCE) of 5.9% and a high AVT of 62%. The energy loss associated with the SJ ST‐PVs is further reduced with a tandem architecture, which affords a high PCE of 10.7%, an AVT of 52.91%, and a light utilization efficiency up to 5.66%. These results represent the best balance of AVT and PCE among all ST‐PVs reported so far, and this design should pave the road for solar windows of high performance.     

Efficient and Stable CsPbI3 Solar Cells via Regulating Lattice Distortion with Surface Organic Terminal Groups

All‐inorganic cesium lead iodide perovskites (CsPbI₃) are promising wide‐bandgap materials for use in the perovskite/silicon tandem solar cells, but they easily undergo a phase transition from a cubic black phase to an orthorhombic yellow phase under ambient conditions. It is shown that this phase transition is triggered by moisture that causes distortion of the corner‐sharing octahedral framework ([PbI₆]^4?). Here, a novel strategy to suppress the octahedral tilting of [PbI₆]^4? units in cubic CsPbI₃ by systematically controlling the steric hindrance of surface organic terminal groups is provided. This steric hindrance effectively prevents the lattice distortion and thus increases the energy barrier for phase transition. This mechanism is verified by X‐ray diffraction measurements and density functional theory calculations. Meanwhile, the formation of an organic capping layer can also passivate the surface electronic trap states of perovskite absorber. These modifications contribute to a stable power conversion efficiency (PCE) of 13.2% for the inverted planar perovskite solar cells (PSCs), which is the highest efficiency achieved by the inverted‐structure inorganic PSCs. More importantly, the optimized devices retained 85% of their initial PCE after aging under ambient conditions for 30 days.