Molecular Dipole Engineering of Carbonyl Additives for Efficient and Stable Perovskite Solar Cells

Carbonyl functional materials as additives are extensively applied to reduce the defects density of the perovskite film. However, there is still a lack of comprehensive understanding for the effect of carbonyl additives to improve device performance. In this work, we systematically study the effect of carbonyl additive molecules on the passivation of defects in perovskite films. After a comprehensive investigation, the results confirm the importance of molecular dipole in amplifying the passivation effect of additive molecules. The additive with strong molecular dipole possesses the advantages of enhancing the efficiency and stability of perovskite solar cells (PSCs). After optimization, the companion efficiency of PSCs is 23.20 %, and it can maintain long-term stability under harsh conditions. Additionally, a large-area solar cell module-modified DLBA was 20.18 % (14 cm²). This work provides an important reference for the selection and designing of efficient carbonyl additives.     

When Aggregation-Induced Emission Meets Perovskites: Efficient Defect-Passivation and Charge-Transfer for Ambient Fabrication of Perovskite Solar Cells

The intrinsic defects in perovskite film can serve as non-radiative recombination center to limit the performance and stability of metal halide perovskite solar cells (PSCs). The additive engineering in perovskite film is always applied to produce high-efficiency PSCs in recent years. Here, a typical donor-acceptor (D−A) structured aggregation-induced emission (AIE) molecule tetraphenylethene-2-dicyano-methylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TPE-TCF) was introduced into perovskite film. The D−A structure of TPE-TCF molecule provided additional charge transfer channels, contributing to transporting electron of TPE-TCF-based device. The cyano (C≡N) of TPE-TCF can interact with the uncoordinated Pb to from a relatively stable intermediate, PbI₂⋅TPE-TCF, resulting in the slower crystal growth, reduced the defects at the grain boundaries and suppressed carrier recombination. As a consequence, the power conversion efficiency (PCE) of TPE-TCF-modified PSCs achieved a remarkably enhanced from 15.63 to 19.66 % with negligible hysteresis, which was prominent in methylammonium lead iodide-based devices fabricated under ambient condition. Furthermore, the PSCs modified by AIE molecule possessed an outstanding stability and maintain about 86 % of the initial PCE after 300 h storage in air at 25–35 °C with a high relative humidity (RH) of ≈85 %. This work suggests that incorporating AIE molecule into perovskite is a promising strategy for facilitating high-performance PSCs commercialization in ambient environment without glovebox.     

SnO2表面卤化提高钙钛矿太阳能电池光伏性能

钙钛矿太阳能电池(PSCs)成为近几年来迅速发展的新型太阳能电池,其中将SnO₂纳米粒子层用作电子传输层(ETL)的钙钛矿太阳能电池器件得到了广泛的关注。SnO₂有着更低的制备温度,使其具备应用于柔性器件的潜力,但与钙钛矿层能级不匹配等问题限制着其发展。而在界面处加入钝化层,尤其是表面卤化的方法或可解决这一问题。本文综合研究了SnO₂表面卤化对钙钛矿太阳能电池光伏性能的影响,选用四丁基氯化铵(TBAC)、四丁基溴化铵(TBAB)和四丁基碘化铵(TBAI)三种钝化材料对SnO₂表面进行钝化处理,并对钝化材料溶液进行了浓度梯度研究。通过材料形貌、结构和光学性能表征以及电池器件性能测试分析等方法,证明了SnO₂表面卤化可提高钙钛矿层的质量和PSCs光伏性能,并从器件内部电荷传输动力学等角度解释了器件性能改善的原因。为进一步说明其性能改善的机理,采用基于密度泛函理论(DFT)的第一性原理计算方法对材料表面性质进行了深入研究,从能量、结构、电荷密度、态密度、功函数等角度解释了表面卤化提高SnO₂/钙钛矿界面处电子传输特性的原因。实验和理论计算均表明TBAC对于SnO₂具有较好的钝化效果,并随着溶液浓度的提升钝化作用越明显。SnO₂表面卤化作用的深入研究不仅对提高电池器件性能具有实际意义,还能够帮助理解太阳能电池界面现象,为界面改性提供新的研究思路。     

A Multifunctional Polymer as an Interfacial Layer for Efficient and Stable Perovskite Solar Cells

Metal-cation defects and halogen-anion defects in perovskite films are critical to the efficiency and stability of perovskite solar cells (PSCs). In this work, a random polymer, poly(methyl methacrylate-co-acrylamide) (PMMA-AM), was synthesized to serve as an interfacial passivation layer for synergistically passivating the under-coordinated Pb²⁺ and anchor the I^- of the [PbI₆]⁴⁻ octahedron. Additionally, the interfacial PMMA-AM passivation layer cannot be destroyed during the hole transport layer deposition because of its low solubility in chlorobenzene. This passivation leads to an enhancement in the open-circuit voltage from 1.12 to 1.22 V and improved stability in solar cell devices, with the device maintaining 95 % of the initial power conversion efficiency (PCE) over 1000 h of maximum power point tracking. Additionally, a large-area solar cell module was fabricated using this approach, achieving a PCE of 20.64 %.     

界面钝化策略:提高钙钛矿太阳能电池的稳定性

近年来,新兴起的有机无机杂化钙钛矿太阳能电池突飞猛进,在短短十年里其光电转化效率从3.8%迅速发展到目前25.2%的认证效率,被视为最具有应用潜力的新型高效率太阳能电池之一。虽然钙钛矿太阳能电池具有很高的光电转换效率已与多晶硅薄膜电池相媲美,但是电池的长期稳定性仍是阻碍其商业化的一大挑战。钙钛矿表面和晶界存在大量的缺陷,界面钝化来提高钙钛矿太阳能电池的稳定性是非常重要且有效的策略。二维钙钛矿材料是有机胺层与无机层交替的层状钙钛矿,具有体积较大的有机铵阳离子,与传统的三维钙钛矿材料相比对于环境的稳定性较好,并且结构灵活可调,在三维钙钛矿表面修饰二维钙钛矿层钝化缺陷,在提高钙钛矿太阳能电池效率的同时又保证了稳定性,另外,合适的钝化剂分子也能够非常有效地钝化缺陷。本文总结了钙钛矿太阳能电池的不稳定因素,归纳了钙钛矿太阳能电池界面钝化方面的研究进展,指出了二维钙钛矿材料发展的巨大潜力以及寻找合适钝化剂分子的原则,期望能够为获得高性能的钙钛矿太阳能电池进而实现商业化提供有益的指导。     

Dual-Interface Engineering in Perovskite Solar Cells with 2D Carbides

Passivating the interfaces between the perovskite and charge transport layers is crucial for enhancing the power conversion efficiency (PCE) and stability in perovskite solar cells (PSCs). Here we report a dual-interface engineering approach to improving the performance of FA_0.85MA_0.15Pb(I_0.95Br_0.05)₃-based PSCs by incorporating Ti₃C₂Cl_x Nano-MXene and o-TB-GDY nanographdiyne (NanoGDY) into the electron transport layer (ETL)/perovskite and perovskite/ hole transport layer (HTL) interfaces, respectively. The dual-interface passivation simultaneously suppresses non-radiative recombination and promotes carrier extraction by forming the Pb−Cl chemical bond and strong coordination of π-electron conjugation with undercoordinated Pb defects. The resulting perovskite film has an ultralong carrier lifetime exceeding 10 μs and an enlarged crystal size exceeding 2.5 μm. A maximum PCE of 24.86 % is realized, with an open-circuit voltage of 1.20 V. Unencapsulated cells retain 92 % of their initial efficiency after 1464 hours in ambient air and 80 % after 1002 hours of thermal stability test at 85 °C.     

Structurally-tuned benzo[1,2-b:4,5:b']dithiophene-based polymer as a dopant-free hole transport material for perovskite solar cells

For highly efficient and stable perovskite solar cells (PSCs), hole transport material (HTM) should be designed and synthesized to afford suitable energy levels, high charge transport, efficient passivation ability, and high device stability. Here, we systematically modulated benzo[1,2-b:4,5:b']dithiophene-based polymer by finely controlling the thienyl and pyridyl contents within the conjugated backbone in order to develop a high performance dopant-free HTM for PSCs. We found that the optimized copolymer with 25% of pyridine content exhibits improved energy level, charge transport, and morphology compared with control homopolymers. As a result, remarkably high power conversion efficiencies up to 21.1% were achieved by employing the optimized polymer as a dopant-free HTM in PSCs.     

Inorganic p-type semiconductors and carbon materials based hole transport materials for perovskite solar cells

Incorporation of proper inorganic p-type semiconductors as hole transport layer has great potential to increase long-term stability while maintaining high power conversion efficiency of perovskite solar cells with low material cost.     

全无机钙钛矿太阳电池的制备及稳定性

全无机钙钛矿太阳电池因其热稳定性好、载流子迁移率高,可用于制备叠层电池等优点备受关注。随着人们对全无机钙钛矿太阳电池的深入研究和制备工艺的持续优化,全无机钙钛矿太阳电池的光电转换效率已经突破19%。然而,全无机钙钛矿材料相稳定性较差,这使得实现全无机钙钛矿太阳电池在空气环境下制备和长期使用面临巨大挑战。众多科研工作者通过分析全无机钙钛矿材料的相变机制,有针对性地提出了包括添加剂工程、界面工程和开发全无机钙钛矿量子点电池等多种方式来改善全无机钙钛矿太阳电池的长期稳定性。本综述从全无机钙钛矿材料与电池的结构、活性层制备方法和稳定性研究三个方面总结了近年来关于全无机钙钛矿太阳电池的研究进展。     

Material and Interface Engineering for High‐Performance Perovskite Solar Cells: A Personal Journey and Perspective

Hybrid organic‐inorganic perovskite solar cells (PSCs) have become a shining star in the photovoltaic field due to their spectacular increase in power conversion efficiency (PCE) from 3.8 % to over 23 % in just few years, opening up the potential in addressing the important future energy and environment issues. The excellent photovoltaic performance can be attributed to the unique properties of the organometal halide perovskite materials, including high absorption coefficient, tunable bandgap, high defect tolerance, and excellent charge transport characteristics. The authors entered this field when pursuing research on dye‐sensitized solar cells (DSCs) by leveraging nanorods arrays for vectorial transport of the extracted electrons. Soon after, we and others realized that while the organometal halide perovskite materials have excellent intrinsic properties for solar cells, interface engineering is at least equally important in the development of high‐performance PSCs, which includes surface defect passivation, band alignment, and heterojunction formation. Herein, we will address this topic by presenting the historical development and recent progress on the interface engineering of PSCs primarily of our own group. This review is mainly focused on the material and interface design of the conventional n‐i‐p, inverted p‐i‐n and carbon electrode‐based structure devices from our own experience and perspective. Finally, the challenges and prospects of this area for future development will also be discussed.     

Recent studies on small molecular and polymeric hole-transporting materials for high-performance perovskite solar cells

A decade of significant research has led to the emergence of photovoltaic solar cells based on perovskites that have achieved an exceptionally high-power conversion efficiency of 26.08%. A key breakthrough in perovskite solar cells (PSCs) occurred when solid hole-transporting materials (HTMs) replaced liquid electrolytes in dye-sensitized solar cells (DSSCs), because HTMs play a crucial role in improving photovoltaic performance as well as cell stability. This review is mainly focused on the HTMs that are responsible for hole transport and extraction in PSCs, which is one of the crucial components for efficient devices. Here, we have reviewed small molecular as well as polymeric HTMs that have been reported in the last two years and discussed their performance based on the analysis of their molecular architectures. Finally, we include a perspective on the molecular engineering of new functional HTMs for highly efficient stable PSCs.     

钙钛矿太阳能电池电子传输层的制备及应用

目前,有机-无机杂化钙钛矿太阳能电池(PSC)的器件效率已经超过25%。电子传输层作为PSC中的重要组成部分在提取和传输光生电子,阻挡空穴,修饰界面,调节界面能级和减少电荷复合等方面起着关键作用。无机n型材料,例如TiO₂、ZnO、SnO₂和其他金属氧化物材料具有成本低和稳定性好的特点,经常在传统PSC中被用作电子传输层(ETL)。有机n型材料,例如富勒烯及其衍生物、萘二酰亚胺聚合物和小分子,具有良好的成膜性能及强的电子传输性能,经常在反式PSC中被用作ETL。本综述详细介绍了PSC中电子传输层的作用机理和制备方法;重点总结了金属氧化物材料、有机分子材料、复合材料和多层分子材料电子传输层和其改性手段的最新研究进展;最后,展望了电子传输层材料朝着高性能PSC的实际应用和发展前景。     

‘Radicalize’ the Performance of Perovskite Solar Cells with Radical Compounds

Perovskite solar cells(PSCs) have attracted tremendous attention due to their outstanding performance within a short development. Radical molecules with unpaired single electrons have been widely used in energy-related fields, such as organic light-emitting diodes(OLEDs), organic field-effect transistors(OFETs), organic and dye-sensitized solar cells, batteries, thermoelectric conversion devices, etc. However, as far as we know, there has never been a systemic collection and analysis of the application of radical molecules in PSCs. Herein, we summarized the role of the radical molecule on perovskite(passivate trap defects, enhance oxygen stability and make perovskite band-bending) and charge transport layer(improve conductivity and mobility, enhance oxygen stability, modulate work function and decrease by-product generating). Meanwhile, future directions of making full use of radical molecules in improving the performances of PSCs were envisioned.     

Perovskite solar cells: Thermal and chemical stability improvement,and economic analysis

Perovskite solar cells (PSCs) are highly efficient and are comparatively cheaper than the large silicon crystals primarily used in solar cells. Their outstanding photovoltaic performance makes them a potential alternative to silicon solar cells. While efficiency and photovoltaic performance have been investigated in recent decades, a knowledge gap on the degradation, economic feasibility and stability of PSCs exists, and their poor stability remains a barrier to commercialization. Thus, this review aims to fill this knowledge gap by focusing on approaches to improve PSCs’ thermal and chemical stability, and their economic viability under different conditions. The structure and manufacture of PSCs are also discussed along with an economic analysis of different perovskite devices. Improvements in thermal stability can be reached by incorporating inorganic materials into the PSC. A PSC model optimized with ZnO improves chemical stability by 8% and works well under low temperatures. To make PSCs more economically feasible, certain parts like counter electrodes (CE) and hole transport materials (HTMs) can be replaced with alternative elements like carbon and inorganic HTMs, respectively. PSCs with long durability and high conversion efficiency will expand the commercial prospects for this material. To bridge the lack of knowledge, further investigation is required on the sustainability and longevity of PSCs.     

Tetra‐ammonium Zinc Phthalocyanine to Construct a Graded 2D–3D Perovskite Interface for Efficient and Stable Solar Cells

The crystallographic defects inevitably incur during the solution processed organic‐inorganic hybrid perovskite film, especially at surface and the grain boundaries (GBs) of perovskite film, which can further result in the reduced cell performance and stability of perovskite solar cells (PSCs). Here, a simple defect passivation method was employed by treating perovskite precursor film with a hydrophobic tetra‐ammonium zinc phthalocyanine (ZnPc). The results demonstrated that a 2D‐3D graded perovskite interface with a capping layer of 2D (ZnPc)_0.5MA_n ? 1Pb_nI_3n + 1 perovskite together with 3D MAPbI₃ perovskite was successfully constructed on the top of 3D perovskite layer. This situation realized the efficient GBs passivation, thus reducing the defects in GBs. As expected, the corresponding PSCs with modified perovskite revealed an improved cell performance. The best efficiency reached 19.6%. Especially, the significantly enhanced long‐term stability of the responding PSCs against humidity and heating was remarkably achieved. Such a strategy in this work affords an efficient method to improve the stability of PSCs and thus probably brings the PSCs closer to practical commercialization.     

Observing Defect Passivation of the Grain Boundary with 2-Aminoterephthalic Acid for Efficient and Stable Perovskite Solar Cells

Metal halide perovskite solar cells (PSCs), with their exceptional properties, show promise as photoelectric converters. However, defects in the perovskite layer, particularly at the grain boundaries (GBs), seriously restrict the performance and stability of PSCs. Now, a simple post-treatment procedure involves applying 2-aminoterephthalic acid to the perovskite to produce efficient and stable PSCs. By optimizing the post-treatment conditions, we created a device that achieved a remarkable power conversion efficiency (PCE) of 21.09 % and demonstrated improved stability. This improvement was attributed to the fact that the 2-aminoterephthalic acid acted as a cross-linking agent that inhibited the migration of ions and passivated the trap states at GBs. These findings provide a potential strategy for designing efficient and stable PSCs regarding the aspects of defect passivation and crystal growth.     

Molecular Ferroelectrics-Driven High-Performance Perovskite Solar Cells

The nonradiative recombination of electrons and holes has been identified as the main cause of energy loss in hybrid organic–inorganic perovskite solar cells (PSCs). Sufficient built-in field and defect passivation can facilitate effective separation of electron–hole pairs to address the crucial issues. For the first time, we introduce a homochiral molecular ferroelectric into a PSC to enlarge the built-in electric field of the perovskite film, thereby facilitating effective charge separation and transportation. As a consequence of similarities in ionic structure, the molecular ferroelectric component of the PSC passivates the defects in the active perovskite layers, thereby inducing an approximately eightfold enhancement in photoluminescence intensity and reducing electron trap-state density. The photovoltaic molecular ferroelectric PSCs achieve a power conversion efficiency as high as 21.78 %.     

Observing Defect Passivation of the Grain Boundary with 2‐Aminoterephthalic Acid for Efficient and Stable Perovskite Solar Cells

Metal halide perovskite solar cells (PSCs), with their exceptional properties, show promise as photoelectric converters. However, defects in the perovskite layer, particularly at the grain boundaries (GBs), seriously restrict the performance and stability of PSCs. Now, a simple post‐treatment procedure involves applying 2‐aminoterephthalic acid to the perovskite to produce efficient and stable PSCs. By optimizing the post‐treatment conditions, we created a device that achieved a remarkable power conversion efficiency (PCE) of 21.09 % and demonstrated improved stability. This improvement was attributed to the fact that the 2‐aminoterephthalic acid acted as a cross‐linking agent that inhibited the migration of ions and passivated the trap states at GBs. These findings provide a potential strategy for designing efficient and stable PSCs regarding the aspects of defect passivation and crystal growth.     

碳基钙钛矿太阳能电池的研究进展

由于具有成本低、工艺简单等优点,有机-无机杂化太阳能电池(PSCs)的研究和发展受到了广泛的关注,光电转换效率也快速提升到与传统晶体硅太阳能电池相当的水平。 然而,PSCs稳定性差的问题严重限制了其商业化。 在各种PSCs中,基于碳电极的无空穴传输层器件(C-PSCs)去除了影响稳定性的有机空穴传输层和金属电极,使得器件稳定性得到了明显的提高,是最具有应用前景的电池器件之一。 自从2013年首次报道以来,C-PSCs的各方面研究取得了很大的进展,效率也从最初的6.6%提高到现在的15.9%。 本综述将系统地介绍C-PSCs的最新研究进展,包括器件结构和工作原理、各部分研究进展(电子传输层、钙钛矿薄膜和碳电极),以及存在的问题和解决方案。     

Highly efficient perovskite solar cells based on symmetric hole transport material constructed with indaceno[1,2-b:5,6-b']dithiophene core building block

Two novel hole transport materials (HTMs) with indaceno[1,2-b:5,6-b']dithiophene (IDT) as core building blocks,termed IDT1 and IDT2,were designed and synthesized.The side alkyl chains were introduced to regulate and control the morphology and stacking behavior of HTMs,and the peripheral triarylamine arms were introduced to adjust the energy levels and to facilitate efficient hole transport.Applied in mesoporous structured perovskite solar cells (PSCs),HTM IDT1 achieved higher power conversion efficiency (PCE,19.55%) and better stability than Spiro-OMeTAD (19.25%) and IDT2 (15.77%) based PSC.These results suggest the potential of IDTl as a promising HTM for PSCs.