反式钙钛矿电池超薄空穴传输层研究进展

空穴传输层(HTLs)厚度对反式钙钛矿太阳能电池(PSCs)性能具有重大影响,因其显著影响太阳光透过和HTLs的空穴传输性能。几个纳米至十几个纳米厚度的超薄HTLs在减少伴生吸收、电荷传输损失和材料消耗等方面具有明显优势。目前,有许多成熟的制备超薄无机HTLs的方法,并在反式和叠层PSCs中得到广泛研究与应用。最近,一些关于有机超薄HTLs的新型制备方法也展现出良好的性能并逐渐引起相关领域研究者关注。在此,本文主要总结反式PSCs中超薄HTLs的研究进展与应用,关注其未来发展的挑战和方向,为该领域进一步的研究提供参考。     

A Solution‐Processable Molecule using Thieno[3,2‐b]thiophene as Building Block for Efficient Organic Solar Cells

A solution‐processed acceptor‐π‐donor‐π‐acceptor (A‐π‐D‐π‐A) type small molecule, namely DCATT, has been designed and synthesized for the application as donor material in organic solar cells. The fused aromatic unit thieno[3,2‐b]thiophene (TT) flanked with thiophene is applied as π bridge, while 4,8‐bisthienyl substituted benzodithiophene (BDT) and 2‐ethylhexyl cyanoacetate are chosen as the central building block and end group, respectively. Introduction of fused ring to the small molecule enhances the conjugation length of the main chain, and gives a strong tendency to form π–π stacking with a large overlapping area which favors to high charge carrier transport. Small‐molecule organic solar cells based on blends of DCATT and fullerene acceptor exhibit power conversion efficiencies as high as 5.20 % under the illumination of AM 1.5G, 100 mW cm^?2.     

Hole‐Transport Materials for Perovskite Solar Cells

The pressure to move towards renewable energy has inspired researchers to look for ideas in photovoltaics that may lead to a major breakthrough. Recently the use of perovskites as a light harvester has lead to stunning progress. The power conversion efficiency of perovskite solar cells is now approaching parity (>22 %) with that of the established technology which took decades to reach this level of performance. The use of a hole transport material (HTM) remains indispensable in perovskite solar cells. Perovskites can conduct holes, but they are present at low levels, and for efficient charge extraction a HTM layer is a prerequisite. Herein we provide an overview of the diverse types of HTM available, from organic to inorganic, in the hope of encouraging further research and the optimization of these materials.     

Lithium Polystyrene Sulfonate as a Hole Transport Material in Inverted Perovskite Solar Cells

Despite the exceptional efficiency of perovskite solar cells (PSCs), further improvements can be made to bring their power conversion efficiencies (PCE) closer to the Shockley-Queisser limit, while the development of cost-effective strategies to produce high-performance devices are needed for them to reach their potential as a widespread energy source. In this context, there is a need to improve existing charge transport layers (CTLs) or introduce new CTLs. In this contribution, we introduced a new polyelectrolyte (lithium poly(styrene sulfonate (PSS))) (Li:PSS) polyelectrolyte as an HTL in inverted PSCs, where Li⁺ can act as a counter ion for the PSS backbone. The negative charge on the PSS backbone can stabilize the presence of p-type carriers and p-doping at the anode. Simple Li:PSS performed poorly due to poor surface coverage and voids existence in perovskite film as well as low conductivity. PEDOT:PSS was added to increase the conductivity to the simple Li:PSS solution before its use which also resulted in lower performance. Furthermore, a bilayer of PEDOT:PSS and Li:PSS was employed, which outperformed simple PEDOT:PSS due to high quality of perovskite film with large grain size also the large electron injection barrier (ϕ_e) impeded back diffusion of electrons towards anode. As a consequence, devices employing PEDOT:PSS / Li:PSS bilayers gave the highest PCE of 18.64%.     

Novel Push-Pull Benzodithiophene-Containing Polymers as Hole-Transport Materials for Efficient Perovskite Solar Cells

Donor-acceptor conjugated polymers are considered advanced semiconductor materials for the development of thin-film electronics. One of the most attractive families of polymeric semiconductors in terms of photovoltaic applications are benzodithiophene-based polymers owing to their highly tunable electronic and physicochemical properties, and readily scalable production. In this work, we report the synthesis of three novel push–pull benzodithiophene-based polymers with different side chains and their investigation as hole transport materials (HTM) in perovskite solar cells (PSCs). It is shown that polymer P3 that contains triisopropylsilyl side groups exhibits better film-forming ability that, along with high hole mobilities, results in increased characteristics of PSCs. Encouraging a power conversion efficiency (PCE) of 17.4% was achieved for P3-based PSCs that outperformed the efficiency of devices based on P1, P2, and benchmark PTAA polymer. These findings feature the great potential of benzodithiophene-based conjugated polymers as dopant-free HTMs for the fabrication of efficient perovskite solar cells.     

界面修饰策略在钙钛矿太阳能电池中的应用

目前钙钛矿太阳能电池的认证效率已达25.2%,被认为是下一代最有希望的薄膜太阳能电池候选者。但通过溶液加工方法制备的钙钛矿薄膜不可控的形貌与较差的结晶性是制约器件稳定性提升和大面积生产的主要原因。为了有效解决这一难题,研究者们通常在电荷传输层与钙钛矿层之间进行界面修饰。本文从界面修饰的角度出发,总结了不同界面修饰策略在钙钛矿太阳能电池中的应用,并展望了界面修饰在低成本和大面积钙钛矿太阳能电池的应用前景。     

有机空穴传输材料在钙钛矿太阳电池中的应用

有机-无机杂化钙钛矿太阳电池(PSCs)由于其诸多优点得到广泛关注,而有机固态空穴传输材料(HTMs)代替液体电解质使其得到飞速的发展,提升了电池的效率和稳定性,已经成为PSCs的重要组成部分。目前应用于PSCs的空穴传输材料分为有机空穴传输材料和无机空穴传输材料两大类。无机空穴传输材料的可选择范围较窄,对应器件的光电转换效率相对较低。开发各类能级匹配、空穴迁移率高的有机空穴传输材料是提高器件效率和稳定性的有效手段,成为相关领域的研究热点。本文依据相对分子质量的大小,将应用于PSCs中的有机空穴传输材料分为小分子类和聚合物类空穴传输材料,详细评述了有机空穴传输材料分子结构对PSCs光电转换效率、填充因子、开路电压、短路电流和稳定性的影响,并对其能级、空穴迁移率的高低、添加剂的使用等进行了讨论。最后详细论述了有机空穴传输材料未来的研究重点和发展趋势。     

An Azaacene Derivative as Promising Electron‐Transport Layer for Inverted Perovskite Solar Cells

It is highly desirable to develop novel n‐type organic small molecules as an efficient electron‐transport layer (ETL) for the replacement of PCBM to obtain high‐performance metal‐oxide‐free, solution‐processed inverted perovskite solar cells (PSCs) because this type of solar cells with a low‐temperature and solution‐based process would make their fabrication more feasible and practical. In this research, the new azaacene QCAPZ has been synthesized and employed as non‐fullerene ETL material for inverted PSCs through a solution‐based process without the need for additional dopants or additives. The as‐fabricated inverted PSCs show a power conversion efficiency up to 10.26 %. Our results clearly suggest that larger azaacenes could be promising electron‐transport materials to achieve high‐performance solution‐processed inverted PSCs.     

反式锡基钙钛矿光伏电池的制备及稳定性策略

近年来,钙钛矿光伏电池（PSCs）取得了突飞猛进的发展,迄今最高认证光电转换效率达到25.7%,但是钙钛矿材料常使用有毒的重金属元素铅,对环境和人体都有极大的危害,不利于其实际应用,因此发展无铅PSCs受到越来越多的关注。锡基钙钛矿材料具有优异的光电性质,特别是带隙窄、载流子迁移率高和激子复合能低,是无铅钙钛矿中最具有潜力的材料。反式（p-i-n型）锡基PSCs由于低迟滞效应、可低温制备及低成本等优点获得普遍关注,取得了一系列重要突破,目前最高效率已经突破14%,具有巨大的发展潜力。鉴于反式锡基钙钛矿太阳能的迅速发展,本文系统综述了反式锡基PSCs制备及稳定性研究进展,尤其关注反式锡基PSCs的界面修饰、锡基钙钛矿材料性能、构筑高质量锡基钙钛矿薄膜的方法以及提高稳定性的策略,并讨论了锡基PSCs的前景展望。     

反式钙钛矿太阳能电池研究进展

反式结构的钙钛矿太阳能电池由于其稳定性好、迟滞效应低等优点越来越受到人们的关注. 自2013年出现以来, 其光电转换效率从最初3.9%快速提升至21.5%. 然而, 反式钙钛矿太阳能电池的光电转化效率相比于传统正置结构钙钛矿太阳能电池依然存在差距, 同时其柔性及空气稳定性和大面积制备技术的开发仍是当前急需亟待解决的难题. 本文就反式钙钛矿太阳能电池载流子传输材料的选择、界面优化及柔性器件的发展等方面进行了系统的综述, 试图总结由结构和材料优化实现反式钙钛矿太阳能电池的高效率、高稳定性、大面积及柔性制备的普遍规律.     

Inkjet-Printed TiO2/Fullerene Composite Films for Planar Perovskite Solar Cells

Perovskite solar cells have garnered and held international research interest, due to ever-climbing power conversion efficiency values, now >25 %. Some high efficiency configurations utilize a compact TiO₂ layer underneath a mesoporous TiO₂ layer, both of which require high temperature annealing steps that could hinder perovskite commercialization. To address the high thermal budget, we chose to use inkjet-printing to combine the two layers into a single TiO₂ film, which incorporates both nanoparticle and molecular precursor as well as organic fullerene additives. We printed the ink on fluorine-doped tin oxide, and after annealing at various temperatures, we found that 400 °C was the optimum annealing temperature for the inkjet-printed electron transport layers, which is significantly lower than the 500 °C required to anneal typical mesoporous TiO₂ films.     

3,4‐Phenylenedioxythiophene (PheDOT) Based Hole‐Transporting Materials for Perovskite Solar Cells

Two new electron‐rich molecules based on 3,4‐phenylenedioxythiophene (PheDOT) were synthesized and successfully adopted as hole‐transporting materials (HTMs) in perovskite solar cells (PSCs). X‐ray diffraction, absorption spectra, photoluminescence spectra, electrochemical properties, thermal stabilities, hole mobilities, conductivities, and photovoltaic parameters of PSCs based on these two HTMs were compared with each other. By introducing methoxy substituents into the main skeleton, the energy levels of PheDOT‐core HTM were tuned to match with the perovskite, and its hole mobility was also improved (1.33×10^?4 cm² V^?1 s^?1, being higher than that of spiro‐OMeTAD, 2.34×10^?5 cm² V^?1 s^?1). The PSC based on MeO‐PheDOT as HTM exhibits a short‐circuit current density (J_sc) of 18.31 mA cm^?2, an open‐circuit potential (V_oc) of 0.914 V, and a fill factor (FF) of 0.636, yielding an encouraging power conversion efficiency (PCE) of 10.64 % under AM 1.5G illumination. These results give some insight into how the molecular structures of HTMs affect their performances and pave the way for developing high‐efficiency and low‐cost HTMs for PSCs.     

Recent Advances in Flexible Perovskite Solar Cells: Fabrication and Applications

Flexible perovskite solar cells have attracted widespread research effort because of their potential in portable electronics. The efficiency has exceeded 18 % owing to the high‐quality perovskite film achieved by various low‐temperature fabrication methods and matching of the interface and electrode materials. This Review focuses on recent progress in flexible perovskite solar cells concerning low‐temperature fabrication methods to improve the properties of perovskite films, such as full coverage, uniform morphology, and good crystallinity; demonstrated interface layers used in flexible perovskite solar cells, considering key figures‐of‐merit such as high transmittance, high carrier mobility, suitable band gap, and easy fabrication via low‐temperature methods; flexible transparent electrode materials developed to enhance the mechanical stability of the devices; mechanical and long‐term environmental stability; an outlook of flexible perovskite solar cells in portable electronic devices; and perspectives of commercialization for flexible perovskite solar cells based on cost.     

A Simple 3,4‐Ethylenedioxythiophene Based Hole‐Transporting Material for Perovskite Solar Cells

We report a novel electron‐rich molecule based on 3,4‐ethylenedioxythiophene (H101). When used as the hole‐transporting layer in a perovskite‐based solar cell, the power‐conversion efficiency reached 13.8 % under AM 1.5G solar simulation. This result is comparable with that obtained using the well‐known hole transporting material 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (spiro‐OMeTAD). This is the first heterocycle‐containing material achieving >10 % efficiency in such devices, and has great potential to replace the expensive spiro‐OMeTAD given its much simpler and cheaper synthesis.     

Isomeric N‐Annulated Perylene Diimide Dimers for Organic Solar Cells

Two isomeric N‐annulated perylene diimide dimers, namely, p‐BDNP and m‐BDNP were designed and synthesized via geometric tuning. The distinct molecular geometry and packing arrangements of isomers with almost identical optical and electrochemical properties rendered us an in‐depth understanding of the molecular structure–aggregation state–photovoltaic performance relationship. Blended with the commercially available donor PCE‐10, p‐BDNP and m‐BDNP showed distinct differences in photovoltaic performance with power conversion efficiencies (PCEs) of 5.01 % and 4.15 %, respectively.     

钙钛矿型太阳电池研究进展

自从2009年钙钛矿材料被应用到太阳电池领域,到现在仅6年的时间里,钙钛矿型太阳电池的光伏转换效率从约3%提高到20.1%,受到全球瞩目。 本文对近年来钙钛矿型太阳电池的发展进行了综述,介绍了钙钛矿吸光材料的性能及其制备,总结了钙钛矿型太阳电池器件结构及其内在机理,探讨了该类型电池待突破的方向和可能的解决途径,阐述了钙钛矿型太阳电池的进展历程,展望了未来发展方向。     

A peri-Xanthenoxanthene Centered Columnar-Stacking Organic Semiconductor for Efficient,Photothermally Stable Perovskite Solar Cells

Modulating the structure and property of hole-transporting organic semiconductors is of paramount importance for high-efficiency and stable perovskite solar cells (PSCs). This work reports a low-cost peri-xanthenoxanthene based small-molecule P1, which is prepared at a total yield of 82 % using a three-step synthetic route from the low-cost starting material 2-naphthol. P1 molecules stack in one-dimensional columnar arrangement characteristic of strong intermolecular π–π interactions, contributing to the formation of a solution-processed, semicrystalline thin-film exhibiting one order of magnitude higher hole mobility than the amorphous one based on the state-of-the art hole-transporter, 2,2-7,7-tetrakis(N,N′-di-paramethoxy-phenylamine 9,9′-spirobifluorene (spiro-OMeTAD). PSCs employing P1 as the hole-transporting layer attain a high efficiency of 19.8 % at the standard AM 1.5 G conditions, and good long-term stability under continuous full sunlight exposure at 40 °C.     

Influence of Alkoxy Chain Length on the Properties of Two-Dimensionally Expanded Azulene-Core-Based Hole-Transporting Materials for Efficient Perovskite Solar Cells

A series of two-dimensionally expanded azulene-core-based π systems have been synthesized with different alkyl chain lengths in the alkoxy moieties connected to the partially oxygen-bridged triarylamine skeletons. The thermal, photophysical, and electronic properties of each compound were evaluated to determine the influence of the alkyl chain length on their effectiveness as hole-transporting materials (HTMs) in perovskite solar cells (PSCs). All the synthesized molecules showed promising material properties, including high solubility, the formation of flat and amorphous films, and optimal alignment of energy levels with perovskites. In particular, the derivatives with methyl and n-butyl in the side chains retained amorphous stability up to 233 and 159 °C, respectively. Such short alkoxy chains also resulted in improved electrical device properties. The PSC device fabricated with the HTM with n-butyl side chains showed the best performance with a power conversion efficiency of 18.9 %, which compares favorably with that of spiro-OMeTAD-based PSCs (spiro-OMeTAD=2,2′,7,7′-tetrakis[N,N-bis(p-methoxyphenyl)amino]-9,9′-spirobifluorene).     

A Supramolecular Complex in Small-Molecule Solar Cells based on Contorted Aromatic Molecules

"Ball and socket" motif: The contorted dibenzotetrathienocoronene (6-DBTTC) forms a complex with the C(70) fullerene PC(70) BM embedded in an amorphous phase of PC(70) BM. The materials are processable into organic solar cells in solution. The power conversion efficiency is maximal when there is a 1:2 molar ratio of 6-DBTTC to PC(70) BM. Formation of the supramolecular complex directly affects charge separation in the active layer.     

Polycyclic Arenes Dihydrodinaphthopentacene-based Hole-Transporting Materials for Perovskite Solar Cells Application

In this paper, two D-π-D type compounds, C1 and C2 , containing dihydrodinaphthopentacene (DHDNP) as a π-bridge, p-methoxydiphenylamine and p-methoxytriphenylamine groups as the donor groups were synthesized. The four 4-hexylphenyl groups at the sp³-carbon bridges of DHDNP were acquainted with control morphology and improving solubility. The light absorption, energy level, thermal properties, and application as hole-transporting materials in perovskite solar cells of these compounds were fully investigated. The HOMO/LUMO levels and energy gaps of these DHDNP-based molecules are suitable for use as hole-transporting materials in PSCs. The best power conversion efficiencies of the PVSCs based on the C1 and C2 are 15.96% and 12.86%, respectively. The performance of C1 is comparable to that of the reference compound spiro-OMeTAD (16.38%). Compared with spiro-OMeTAD, the C1 -based PVSC device showed good stability, which was slightly decreased to 98.68% of its initial efficiency after 48 h and retained 81% of its original PCE after 334 h without encapsulation. These results reveal the potential usefulness of the DHDNP building block for further development of economical and highly efficient HTMs for PVSCs.