Investigation of NiO<Subscript>x</Subscript>-hole transport layers in triple cation perovskite solar cells

Perovskite solar cells with a planar p-i-n device structure offer easy processability at low temperatures, suitable for roll-to-roll fabrication on flexible substrates. Herein we investigate different hole transport layers (solution processed NiO_x, sputtered NiO_x, PEDOT:PSS) in planar p-i-n perovskite solar cells using the triple cation lead halide perovskite Cs_0.08(MA_0.17FA_0.83)_0.92Pb(I_0.83Br_0.17)₃ as absorber layer. Overall, reproducible solar cell performances with power conversion efficiencies up to 12.8% were obtained using solution processed NiO_x as hole transport layer in the devices. Compared to that, devices with PEDOT:PSS as hole transport layer yield efficiencies of approx. 8.4%. Further improvement of the fill factor was achieved by the use of an additional zinc oxide nanoparticle layer between the PC₆₀BM film and the Ag electrode.     

Efficient Flexible Solar Cell based on Composition‐Tailored Hybrid Perovskite

Organic–inorganic hybrid perovskites (OIHPs) are new photoactive layer candidates for lightweight and flexible solar cells due to their low‐temperature process capability; however, the reported efficiency of flexible OIHP devices is far behind those achieved on rigid glass substrates. Here, it is revealed that the limiting factor is the different perovskite film deposition conditions required to form the same film morphology on flexible substrates. An optimized perovskite film composition needs a different precursor ratio, which is found to be essential for the formation of high‐quality perovskite films with longer radiative carrier recombination lifetime, smaller density of trap states, reduced precursor residue, and uniform and pin‐hole free films. A record efficiency of 18.1% is achieved for the flexible perovskite solar‐cell devices made on an indium tin oxide/poly(ethylene terephthalate) substrate via a low temperature (≤100 °C) solution process.     

钙钛矿太阳能电池的研究进展

钙钛矿太阳能电池由纳米晶致密层、钙钛矿型光活性层CH₃NH₃PbX₃ (X= Cl、Br、I)、空穴传输层及对电极组成。其中光活性层吸光材料的种类及其成膜技术、空穴传输层材料类型及结构设计是影响钙钛矿太阳能电池光电性能的重要因素。本文结合钙钛矿太阳能电池近年来的最新研究进展, 对影响器件光电性能的关键因素: 光吸收层、空穴传输层、工艺参数以及结构设计等进行综述, 同时展望了钙钛矿太阳能电池未来的发展趋势。     

NiO层作为空穴传输层的钙钛矿太阳能电池的制备和性能研究

有机-无机杂化钙钛矿太阳能电池因具有光吸收强、载流子扩散长度长等优点,近年来在光伏领域吸引了广泛的关注,其中,无机NiO薄膜在电池结构中作为空穴传输层已发展成为钙钛矿电池研究的重要方向。采用溶液旋涂法制备了NiO薄膜,系统优化了不同烧结温度和不同浓度条件下NiO薄膜对钙钛矿电池性能的影响。采用扫描电镜、X射线衍射、紫外-可见分光光度计、电流-电压测试、光量子效率等方法分别观察和分析了NiO薄膜以及相应电池的光电性能。结果表明:溶液旋涂法制备的NiO薄膜具有良好的覆盖性、非常低的表面粗糙度,当制备NiO的预制溶液浓度为0.05mol/L,NiO的烧结温度为500℃时,获得了最优的电池性能,最高电池转换效率为14.62%。     

Ultraflexible and Lightweight Bamboo‐Derived Transparent Electrodes for Perovskite Solar Cells

Wearable devices are mainly based on plastic substrates, such as polyethylene terephthalate and polyethylene naphthalate, which causes environmental pollution after use due to the long decomposition periods. This work reports on the fabrication of a biodegradable and biocompatible transparent conductive electrode derived from bamboo for flexible perovskite solar cells. The conductive bioelectrode exhibits extremely flexible and light‐weight properties. After bending 3000 times at a 4 mm curvature radius or even undergoing a crumpling test, it still shows excellent electrical performance and negligible decay. The performance of the bamboo‐based bioelectrode perovskite solar cell exhibits a record power conversion efficiency (PCE) of 11.68%, showing the highest efficiency among all reported biomass‐based perovskite solar cells. It is remarkable that this flexible device has a highly bendable mechanical stability, maintaining over 70% of its original PCE during 1000 bending cycles at a 4 mm curvature radius. This work paves the way for perovskite solar cells toward comfortable and environmentally friendly wearable devices.     

Interface engineering of high efficiency perovskite solar cells based on ZnO nanorods using atomic layer deposition

Despite the considerably improved efficiency of inorganic-organic metal hybrid perovskite solar cells (PSCs),electron transport is still a challenging issue.In this paper,we report the use of ZnO nanorods prepared by hydrothermal selfassembly as the electron transport layer in perovskite solar cells.The efficiency of the perovskite solar cells is significantly enhanced by passivating the interfacial defects via atomic layer deposition of A12O3 monolayers on the ZnO nanorods.By employing the A12O3 monolayers,the average power conversion efficiency of methylammonium lead iodide PSCs was increased from 10.33％ to 15.06％,and the highest efficiency obtained was 16.08％.We suggest that the passivation of defects using the atomic layer deposition of monolayers might provide a new pathway for the improvement of all types of PSCs..     

Record Efficiency Stable Flexible Perovskite Solar Cell Using Effective Additive Assistant Strategy

Even though the power conversion efficiency (PCE) of rigid perovskite solar cells is increased to 22.7%, the PCE of flexible perovskite solar cells (F‐PSCs) is still lower. Here, a novel dimethyl sulfide (DS) additive is developed to effectively improve the performance of the F‐PSCs. Fourier transform infrared spectroscopy reveals that the DS additive reacts with Pb²⁺ to form a chelated intermediate, which significantly slows down the crystallization rate, leading to large grain size and good crystallinity for the resultant perovskite film. In fact, the trap density of the perovskite film prepared using the DS additive is reduced by an order of magnitude compared to the one without it, demonstrating that the additive effectively retards transformation kinetics during the thin film formation process. As a result, the PCE of the flexible devices increases to 18.40%, with good mechanical tolerance, the highest reported so far for the F‐PSCs. Meanwhile, the environmental stability of the F‐PSCs significantly enhances by 1.72 times compared to the device without the additive, likely due to the large grain size that suppresses perovskite degradation at grain boundaries. The present strategy will help guide development of high efficiency F‐PSCs for practical applications.     

Manipulating the Mixed‐Perovskite Crystallization Pathway Unveiled by In Situ GIWAXS

Mixed perovskites have achieved substantial successes in boosting solar cell efficiency, but the complicated perovskite crystal formation pathway remains mysterious. Here, the detailed crystallization process of mixed perovskites (FA_0.83MA_0.17Pb(I_0.83Br_0.17)₃) during spin‐coating is revealed by in situ grazing‐incidence wide‐angle X‐ray scattering measurements, and three phase‐formation stages are identified: I) precursor solution; II) hexagonal δ‐phase (2H); and III) complex phases including hexagonal polytypes (4H, 6H), MAI–PbI₂–DMSO intermediate phases, and perovskite α‐phase. The correlated device performance and ex situ characterizations suggest the existence of an “annealing window” covering the duration of stage II. The spin‐coated film should be annealed within the annealing window to avoid the formation of hexagonal polytypes during the perovskite crystallization process, thus achieving a good device performance. Remarkably, the crystallization pathway can be manipulated by incorporating Cs⁺ ions in mixed perovskites. Combined with density functional theory calculations, the perovskite system with sufficient Cs⁺ will bypass the formation of secondary phases in stage III by promoting the formation of α‐phase both kinetically and thermodynamically, thereby significantly extending the annealing window. This study provides underlying reasons of the time sensitivity of fabricating mixed‐perovskite devices and insightful guidelines for manipulating the perovskite crystallization pathways toward higher performance.     

Realizing Reduced Imperfections via Quantum Dots Interdiffusion in High Efficiency Perovskite Solar Cells

Realization of reduced ionic (cationic and anionic) defects at the surface and grain boundaries (GBs) of perovskite films is vital to boost the power conversion efficiency of organic–inorganic halide perovskite (OIHP) solar cells. Although numerous strategies have been developed, effective passivation still remains a great challenge due to the complexity and diversity of these defects. Herein, a solid-state interdiffusion process using multi-cation hybrid halide perovskite quantum dots (QDs) is introduced as a strategy to heal the ionic defects at the surface and GBs. It is found that the solid-state interdiffusion process leads to a reduction in OIHP shallow defects. In addition, Cs⁺ distribution in QDs greatly influences the effectiveness of ionic defect passivation with significant enhancement to all photovoltaic performance characteristics observed on treating the solar cells with Cs_0.05(MA_0.17FA_0.83)_0.95PbBr₃ (abbreviated as QDs-Cs5). This enables power conversion efficiency (PCE) exceeding 21% to be achieved with more than 90% of its initial PCE retained on exposure to continuous illumination of more than 550 h.     

Efficient light harvesting from flexible perovskite solar cells under indoor white light-emitting diode illumination

This is the first report of an investigation on flexible perovskite solar cells for artificial light harvesting by using a white light-emitting diode (LED) lamp as a light source at 200 and 400 lx,values typically found in indoor environments.Flexible cells were developed using either low-temperature sol-gel or atomiclayer-deposited compact layers over conducting polyethylene terephthalate (PET)substrates,together with ultraviolet (UV)-irradiated nanoparticle TiO2 scaffolds,a CH3NH3PbI3-xClx perovskite semiconductor,and a spiro-MeOTAD hole transport layer.By guaranteeing high-quality carrier blocking (via the 10-40 nm-thick compact layer) and injection (via the nanocrystalline scaffold and perovskite layers) behavior,maximum power conversion efficiencies (PCE) and power densities of 10.8％ and 7.2 μW.cm-2,respectively,at 200 lx,and 12.1％ and 16.0 μW·cm-2,respectively,at 400 lx were achieved.These values are the state-of-the-art,comparable to and even exceeding those of flexible dye-sensitized solar cells under LED lighting,and significantly greater than those for flexible amorphous silicon,which are currently the main flexible photovoltaic technologies commercially considered for indoor applications.Furthermore,there are significant margins of improvement for reaching the best levels of efficiency for rigid glass-based counterparts,which we found was a high of PCE ～24％ at 400 lx.With respect to rigid devices,flexibility brings the advantages of being low cost,lightweight,very thin,and conformal,which is especially important for seamless integration in indoor environments.     

高效率双结钙钛矿叠层太阳能电池研究进展

以钙钛矿电池为顶电池的叠层太阳电池发展迅速,成为太阳能光伏领域的研究热点之一。随着电池结构和制备工艺的优化,叠层电池的光电转换效率快速提升,单片钙钛矿/晶硅叠层电池的效率已达到31.3%。本综述对近年来以宽带隙钙钛矿电池作为顶子电池、晶体硅电池及其他新型中窄带隙电池(钙钛矿电池、有机电池、铜铟镓硒(CIGS)电池)作为底子电池的叠层电池的研究进展进行了系统梳理,总结了叠层电池的顶电池、中间互联层和底电池的材料、结构及光电性能等方面的关键技术及难点,希望能够为进一步提升叠层电池效率提供一些思路。并对未来低成本高效叠层太阳能电池的光学和电学优化需求做出了分析与展望。     

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。     

Critical review of recent progress of flexible perovskite solar cells

Perovskite solar cells (PSCs) have emerged as a ‘rising star’ in recent years due to their high-power conversion efficiency (PCE), extremely low cost and facile fabrication techniques. To date, PSCs have achieved a certified PCE of 25.2% on rigid conductive substrates, and 19.5% on flexible substrates. The significant advancement of PSCs has been realized through various routes, including perovskite composition engineering, interface modification, surface passivation, fabrication process optimization, and exploitation of new charge transport materials. However, compared with rigid counterparts, the efficiency record of flexible perovskite solar cells (FPSCs) is advancing slowly, and therefore it is of great significance to scrutinize recent work and expedite the innovation in this field. In this article, we comprehensively review the recent progress of FPSCs. After a brief introduction, the major features of FPSCs are compared with other types of flexible solar cells in a broad context including silicon, CdTe, dye-sensitized, organic, quantum dot and hybrid solar cells. In particular, we highlight the major breakthroughs of FPSCs made in 2019/2020 for both laboratory and large-scale devices. The constituents of making a FPSC including flexible substrates, perovskite absorbers, charge transport materials, as well as device fabrication and encapsulation methods have been critically assessed. The existing challenges of making high performance and long-term stable FPSCs are discussed. Finally, we offer our perspectives on the future opportunities of FPSCs in the field of photovoltaics.     

Progress in Materials Development for the Rapid Efficiency Advancement of Perovskite Solar Cells

The efficiency of perovskite solar cells (PSCs) has undergone rapid advancement due to great progress in materials development over the past decade and is under extensive study. Despite the significant challenges (e.g., recombination and hysteresis), both the single‐junction and tandem cells have gradually approached the theoretical efficiency limit. Herein, an overview is given of how passivation and crystallization reduce recombination and thus improve the device performance; how the materials of dominant layers (hole transporting layer (HTL), electron transporting layer (ETL), and absorber layer) affect the quality and optoelectronic properties of single‐junction PSCs; and how the materials development contributes to rapid efficiency enhancement of perovskite/Si tandem devices with monolithic and mechanically stacked configurations. The interface optimization, novel materials development, mixture strategy, and bandgap tuning are reviewed and analyzed. This is a review of the major factors determining efficiency, and how further improvements can be made on the performance of PSCs.     

Ultra-smooth CsPbI_2Br film via programmable crystallization process for high-efficiency inorganic perovskite solar cells

CsPbI₂Br is an ideal inorganic perovskite material with a reasonable bandgap for solar cell applications because of its advantage of superior thermal and phase stability. However, the performance of CsPbI2Br based solar cells highly relied on the perovskite crystallization process along with the interfacial contact engineering process between CsPbI₂Br perovskite and charge-transporting layers. In this work, a programmable crystallization method is developed to obtain ultra-smooth CsPbI₂Br perovskite film with a well-engineered contact interface in perovskite solar cells. This method combines a pre-stand-by process with a programmable gradient thermal engineering process, which mediates the crystal growth dynamics process of CsPbI2Br perovskite by controlling the release of dimethyl sulfoxide(DMSO) from its coordinates with the perovskite film, leading to high-quality CsPbI₂Br film with large-scale crystalline grains, reduced surface roughness, and low trap density. Fabricated perovskite devices based on CsPbI₂Br film obtained by this method deliver power conversion efficiency of 14.55 %;meanwhile, the encapsulated CsPbI₂Br perovskite device achieves a maximum efficiency of 15.07 %. This decent solar conversion efficiency demonstrates the effectiveness of the programmable crystallization method used in this work,which shows great potential as a universal approach in obtaining high-quality CsPbI₂Br perovskite films for fabricating high-efficiency inorganic perovskite solar cells.     

柔性染料敏化太阳能电池和柔性钙钛矿太阳能电池关键电极材料研究进展

柔性太阳能电池具有轻便、可弯曲的优点,可用于可穿戴设备等器件的即时充电,具有广阔的应用前景,受到持续广泛的关注。柔性太阳能电池制备中的关键在于基材以及与之相关的电极材料的制备。本文综述了柔性染料敏化太阳能电池和柔性钙钛矿太阳能电池近几年的发展情况,着重介绍了柔性染料敏化太阳能电池光阳极、对电极以及柔性钙钛矿太阳能电池的底电极和电子传输层。结果发现高温烧结目前仍是制备高效染料敏化太阳能电池光阳极不可避免的方法,而对电极则不受这一限制并且已经有多种材料的效率超过了高温烧结的铂。柔性钙钛矿太阳能电池的研究重点是用其他材料代替底电极中柔性较差的ITO以及高温烧结的电子传输材料TiO₂,并且都取得显著成效。在此基础上,展望了柔性染料敏化太阳能电池和柔性钙钛矿太阳能电池未来的发展方向。     

Wearable Large‐Scale Perovskite Solar‐Power Source via Nanocellular Scaffold

Dramatic advances in perovskite solar cells (PSCs) and the blossoming of wearable electronics have triggered tremendous demands for flexible solar‐power sources. However, the fracturing of functional crystalline films and transmittance wastage from flexible substrates are critical challenges to approaching the high‐performance PSCs with flexural endurance. In this work, a nanocellular scaffold is introduced to architect a mechanics buffer layer and optics resonant cavity. The nanocellular scaffold releases mechanical stresses during flexural experiences and significantly improves the crystalline quality of the perovskite films. The nanocellular optics resonant cavity optimizes light harvesting and charge transportation of devices. More importantly, these flexible PSCs, which demonstrate excellent performance and mechanical stability, are practically fabricated in modules as a wearable solar‐power source. A power conversion efficiency of 12.32% for a flexible large‐scale device (polyethylene terephthalate substrate, indium tin oxide‐free, 1.01 cm²) is achieved. This ingenious flexible structure will enable a new approach for development of wearable electronics.     

低维钙钛矿:兼具高效率和稳定性的新型太阳能电池光吸收层候选材料

使用有机无机杂化钙钛矿材料作为光吸收层的钙钛矿太阳能电池自进入人们的视野以来,其制备工艺和器件结构不断得到优化,短短几年内效率取得了非常可观的增长。与此同时,这种基于三维钙钛矿材料的电池的缺点也越来越突出,尤其是材料的不稳定性,严重阻碍了其发展。低维钙钛矿材料具有有机胺层与无机层(金属卤化物钙钛矿晶体)之间相互交替的低维(层状)结构,其中被有机胺隔开的独立钙钛矿层中八面体的层数n越小,钙钛矿越接近二维结构。相比传统三维钙钛矿结构,低维钙钛矿材料应用于光伏器件具有两大优势:(1)耐湿性、光热稳定性大大增强;(2)可以通过改变n和插入的有机胺的种类来实现光学及电学性质的可调性。然而,低维钙钛矿具有较大的光学带隙,有机胺的引入降低了载流子迁移率,导致低维钙钛矿电池的效率明显低于三维钙钛矿电池。因此,近三年来除研究钙钛矿层数对材料性质和器件性能的影响外,研究者们主要从选择合适的有机胺和优化薄膜制备工艺方面不断尝试,并取得了丰硕的成果,在充分发挥低维钙钛矿稳定性优势的同时大幅提升了器件效率。目前,低维钙钛矿太阳能电池的光电转换效率已由2014年的4.37%跃升至13.7%。在较高效率的低维钙钛矿太阳能电池中已取得成功应用的有机胺类包括苯乙胺(PEA)、正丁胺(n-BA)、异丁胺(iso-BA)、聚乙烯亚胺(PEI)等。其中PEA应用得最早;n-BA是运用在目前为止最高效的低维钙钛矿电池中的有机胺;而PEI插层形成的低维钙钛矿拥有相对更小的光学带隙和更高的耐湿性,但载流子的传输会受到更大的限制。低维钙钛矿薄膜的制备起初主要采用简单的一步旋涂法,但此法所得的低维钙钛矿平行于基底生长,器件效率很低。近两年的研究工作将基底预热、浸泡、反溶剂滴加等手段引入到钙钛矿旋涂工艺中,实现了低维钙钛矿优先垂直基底生长,为突破低效率瓶颈提供了可能。此外,以三维钙钛矿为基础,以有机胺为添加剂,制得的二维和三维混合的钙钛矿结构,也可以实现器件效率和稳定性的双提升。本文归纳了低维钙钛矿光伏器件的研究进展,分别对低维钙钛矿的分子结构、插入的有机胺的选择、钙钛矿薄膜的制备方法等进行介绍,分析了低维钙钛矿太阳能电池面临的问题并展望其前景,以期为制备稳定和环境友好的新型钙钛矿太阳能电池提供参考。     

Polarized Ferroelectric Polymers for High‐Performance Perovskite Solar Cells

In hybrid organic–inorganic lead halide perovskite solar cells, the energy loss is strongly associated with nonradiative recombination in the perovskite layer and at the cell interfaces. Here, a simple but effective strategy is developed to improve the cell performance of perovskite solar cells via the combination of internal doping by a ferroelectric polymer and external control by an electric field. A group of polarized ferroelectric (PFE) polymers are doped into the methylammonium lead iodide (MAPbI₃) layer and/or inserted between the perovskite and the hole‐transporting layers to enhance the build‐in field (BIF), improve the crystallization of MAPbI₃, and regulate the nonradiative recombination in perovskite solar cells. The PFE polymer‐doped MAPbI₃ shows an orderly arrangement of MA⁺ cations, resulting in a preferred growth orientation of polycrystalline perovskite films with reduced trap states. In addition, the BIF is enhanced by the widened depletion region in the device. As an interfacial dipole layer, the PFE polymer plays a critical role in increasing the BIF. This combined effect leads to a substantial reduction in voltage loss of 0.14 V due to the efficient suppression of nonradiative recombination. Consequently, the resulting perovskite solar cells present a power conversion efficiency of 21.38% with a high open‐circuit voltage of 1.14 V.     

醋酸铅添加剂在印刷钙钛矿太阳能电池中的应用

印刷钙钛矿太阳能电池采用无机介孔骨架包覆有机无机杂化钙钛矿材料的器件结构,制备工艺简单,原材料成本低廉,且稳定性优异.然而,在介孔骨架中均匀沉积高质量的钙钛矿材料存在一定困难.本研究通过在典型钙钛矿材料甲胺铅碘(MAPbI3)前驱液中引入醋酸铅(Pb(Ac)2)作为添加剂,加快钙钛矿晶体的成核从而改善其在介孔骨架中的生...