Zhiguanggu comprehensive summary series: heavy hit! The latest progress in flexible perovskite photovoltaics in 2024!

• 1. Flexible perovskite solar cells continue to achieve breakthroughs in efficiency

  
  

  1. Joule: Introducing zwitterionic elastomers to achieve high efficiency of flexible perovskite solar cells of 24.51% ( certified 24.04%)

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• On February 8, 2024, Ge Ziyi and others from the Ningbo Institute of Materials, Chinese Academy of Sciences introduced zwitterionic elastomer (SBMA) into the perovskite film and formed an intermediate SBMA-PbI2 adduct through in-situ cross-linking to regulate the formation of perovskite . Nucleation and crystallization. The polar sulfonic acid groups on SBMA provide chemical passivation of perovskite defect vacancies, create a large dielectric environment, shield the carrier capture process, and inhibit non-radiative recombination. The fusion of zwitterionic ions in the cross-linked elastomer located at the grain boundaries endows the flexible perovskite film with the ability to instantaneously self-cure under mild processing conditions (40°C, 15 min). Finally, a record-breaking PCE of 24.51% (certified 24.04%) was obtained , and it exhibited excellent mechanical stability and durability, retaining more than 90% of the initial PCE after 10,000 bending cycles.
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• https://doi.org/10.1016/j.joule.2024.01.021

  
  

  2. EES: Introducing room-temperature self-healing ion-conducting elastomer to achieve high efficiency of 24.84% in flexible perovskite solar cells

  
  

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• On March 6, 2024, Zhou Jun from Zhengzhou University/National Nanocenter, Song Yanlin from the Institute of Chemistry, Chinese Academy of Sciences, Hu Xiaotian from Nanchang University and others designed a room temperature self-healing ion-conducting elastomer (ICE) containing imidazole-based ionic liquid. Due to the high conductivity of ionic liquids and the dynamic covalent disulfide bonds, hydrogen bonds, and metal coordination bonds of elastomers, ICE exhibits excellent elastomer properties and conductivity, and can dynamically self-heal at room temperature (~25 ℃ ). The corresponding ICE was introduced into the perovskite system to achieve real-time self-healing and electrical performance regulation of grain boundary cracks (~25°C) in flexible PSCs. The uniform distribution of ICE at the grain boundaries of perovskite films can effectively regulate crystallization, passivate grain boundary defects, reduce the potential difference between perovskite film grains and grain boundaries, and facilitate the extraction of charge carriers at grain boundaries. and transmission. The stable PCE of ICE -containing PSCs on rigid and flexible substrates were 25.47% and 24.84% (0.04 cm2), respectively. More importantly, the ICE network located at the grain boundaries of the film can not only toughen the perovskite film but also repair grain boundary cracks at room temperature.
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• https://doi.org/10.1039/D4EE00462K

  
  

  2. iEnergy: Constant pH CBD controllable preparation of SnO2 electron transport layer achieves high efficiency of 25.09% for flexible perovskite solar cells ( certified 24.90%)

  
  

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• On March 24, 2024, Yi Chenyi and others from the New Power System Research Center of the Carbon Neutral Institute of Tsinghua University and the Department of Electrical Engineering published in "Electric Power and Energy Transactions (English)" (iEnergy) that 25% was achieved through controlled growth preparation of SnO2 The research results of efficient flexible perovskite solar cells report a high PCE FPSC with controllable growth of SnO2 electron transport layer through constant pH chemical bath deposition (CBD). By using SnSO4 instead of conventional SnCl2 as the tin source, SnO2 films can be grown in a controlled manner under constant pH conditions without adding strong acid, making it suitable for acid-sensitive flexible ITO substrates. Based on a mild and controllable growth environment, a uniform and dense SnO2 film with particle growth was obtained, with high coverage and repeatability. The PCE of FPSCs is as high as 25.09% (certified 24.90%). This efficiency is the highest among currently reported flexible perovskite solar cells. The world's highest efficiency record. And the prepared FPSCs have high durability and can still maintain more than 90% of the initial PCE after 10,000 bending cycles.

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• https://ieeexplore.ieee.org/document/10478316

  
  

  2. Flexible perovskite solar module efficiency continues to break through

  
  

  1. Nat. Photonics: Multifunctional molecular ET realizes high-efficiency flexible perovskite micro-module 20.1% ( certified 19.0%)

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• Flexible perovskite solar cells have attracted widespread attention due to their softness and high power-weight compatibility. However, the low interfacial adhesion and large deformation of flexible substrates lead to poor quality of the perovskite buried-substrate interface, which greatly limits the performance of flexible perovskite solar cells (FPSCs).

  
  

  Huang Jinsong and others from the University of North Carolina reported that the multifunctional molecule Entinonot (ET) improves the mechanical toughness and efficiency of flexible perovskite solar cells and micro-modules. The organic molecule Entinonot (ET) was added to PTAA and perovskite. ET), which enhances the adhesion between the perovskite and the ITO substrate through its interaction with the perovskite and reduces the voids at the bottom interface. At the same time, adding ET to the perovskite precursor helps form a perovskite film with better crystallinity and fewer voids by forming an adduct with lead. The PCE of the prepared F-PSCs and micro-modules were 23.4% and 20.1% respectively (certified 19.0%) . Finally, ET molecules also improve the mechanical durability and operational stability of flexible perovskite micromodules.

  
  

  The paper also identifies several reasons that may hinder the development of efficient flexible perovskite micromodules .

  
  

  1. F-PSCs are prepared on flexible substrates. Commonly used ones are polyethylene terephthalate (PET) and polyethylene naphthalate (PET), while most commercially available flexible indium tin oxide The ITO substrate uses lower-cost PET. Large-area perovskite films can be prepared on rigid substrates using blade coating, slot coating, and roll-to-roll methods. However, since flexible substrates are soft and uneven, it is difficult to coat calcium on large-area flexible substrates. Titanium films are more difficult.

  
  

  2. PET has a low glass transition temperature (Tg) (around 70 °C), making them prone to bending or twisting at common perovskite annealing temperatures (120-150 °C), which is problematic in large-area substrates more obvious. Therefore, the preparation of F-PSC requires a lower annealing temperature, which brings new problems of film crystallization. Voids due to initial residual dimethyl sulfoxide (DMSO) were observed at the buried layer interface between the perovskite and the hole extraction layer, which severely limited the device performance. Lower annealing temperatures result in more DMSO residue, resulting in worse bottom contact.

  
  

  3. Since flexible substrates made of amorphous but smoother ITO tend to have poor adhesion to perovskites, this situation becomes worse when using hydrophobic polymer hole transport materials (HTM) such as PTAA. Worse.

  
  

  4. The thermal expansion coefficient of PET substrate is at least one order of magnitude larger than that of glass and larger than that of perovskite. The larger thermal expansion/shrinkage of flexible substrates during heat treatment can exacerbate this weak interfacial adhesion, leading to mechanical delamination and durability issues in F-PSCs.

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• https://doi.org/10.1038/s41566-023-01373-z

  
  

  2. Joule: New ETL design achieves flexible perovskite module certification efficiency of 16.4% (900 cm2)

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• On February 29, 2024, Seong Sik Shin and others from the Korea Institute of Chemical Technology found that when traditional colloidal SnO2 nanoparticles are used as electron transport layers (ETL), flexible calcium titanium evaporates due to the imbalance between surface coverage and charge transport properties. There is a trade-off between efficiency and stability in f-PSCs. In order to resolve this contradiction, the research team designed a new ETL that enhances charge transfer characteristics and reduces shunt sites, thereby improving efficiency and operational stability. Therefore, f-PSC certification efficiency of 21.8% (22.92% indoor) and f-PSM certification efficiency of 16.4% (900 cm2) were successfully achieved . In addition, it was further found that incomplete coverage can lead to the formation of shunt paths, causing current crowding effects, which may have a significant impact on long-term operational stability.
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• https://doi.org/10.1016/j.joule.2024.02.008

  
  

  3. New progress and latest summary of flexible perovskite photovoltaic industrialization process

  
  

  1. Nat. Commun.: Perovskite solar cell module prepared by full roll-to-roll printing

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• The rapid development of organic-inorganic hybrid perovskite solar cells has enabled laboratory-scale devices with energy conversion efficiencies competitive with commercialized technologies. However, hybrid perovskite solar cells have yet to make an impact outside of the research field, and conversion to large-area devices prepared through industrially relevant manufacturing methods remains a significant challenge.

  
  

  On March 12, 2024, Doojin Vak from the Flexible Electronics Laboratory of the Australian CSIRO Company, Tawfique Hasan from the University of Cambridge in the UK, Jacek J. Jasieniak from Monash University and others reported the preparation of fully R2R printed PSCs with a PCE as high as 15.5%. The article also reports on the use of only industrially relevant R2R manufacturing technology and demonstrates for the first time modules produced in an atmospheric environment. This is achieved by developing: (i) robust and scalable deposition techniques, (ii) perovskite-friendly carbon inks to replace vacuum electrodes, and (iii) R2R-based high-throughput experimental platforms. The latter simulates a manufacturing process that produces and tests thousands of small batteries every day. This enables a seamless transition from microfactory to full-scale R2R manufacturing of modules (active area ~50 cm2) and achieves PCE of up to 11% . Future printing of PSCs can be calculated using cost models by considering manufacturing costs for various production scenarios, based on the production methods and materials used in current work, and the resulting equipment efficiencies.

  
  

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• https://www.nature.com/articles/s41467-024-46016-1

  
  

  2. Joule: Review of large-area flexible perovskite solar energy preparation methods

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• Flexible perovskite solar cells (FPSCs) have attracted widespread attention due to their potential applications. However, despite laboratory-scale efficiencies exceeding 24%, achieving efficient large-area FPSCs remains a challenge. The transition from laboratory research to industrialization level will face many transitional issues, such as scaling up production, maintaining product quality consistency, optimizing material utilization, solving safety issues, and ensuring cost-effectiveness.

  
  

  In view of this, on March 18, 2024, Liu Shengzhong of Shaanxi Normal University, Yang Dong of Dalian Institute of Chemical Physics, Chinese Academy of Sciences, and Wang Kai of Zhejiang University reported a review of preparation processes that promote the development of flexible perovskite solar cells, providing a comprehensive overview of large-area FPSCs and Industrially compatible methods include blade coating, slot coating, spray coating, various printing techniques, solution processes such as evaporative deposition, and other technologies such as atomic layer deposition and magnetron sputtering. It emphasizes the determination of appropriate process parameters for each functional layer through material selection and preparation methods, thereby achieving technological breakthroughs in large-area FPSCs, improving efficiency, and realizing the potential of large-area devices. Additionally, opportunities and challenges related to high-throughput production of flexible perovskite solar modules are discussed.

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• https://doi.org/10.1016/j.joule.2024.02.025

  
  

  3. New applications of flexible perovskite solar cells

  
  

  Nat. Energy: Flexible quasi-2D perovskite solar cells with high specific power and stability for energy autonomous drones

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• Perovskite solar cells are a promising technology for new photovoltaic applications requiring mechanical flexibility and high specific power. However, these devices suffer from poor operational stability.

  
  

  On April 17, 2024, Martin Kaltenbrunner and others from Johann Kepler University Linz reported the research results of flexible quasi-two-dimensional perovskite solar cells with high specific power and high stability for energy autonomous drones. By using α- Methyl benzyl ammonium iodide was introduced into the perovskite light-absorbing layer to develop a quasi-two-dimensional perovskite solar cell that is lightweight, ultra-thin (<2.5 μm), flexible, and a non-oxide transparent electrode. Devices were prepared directly on ultrathin polymer foils coated with an aluminum oxide barrier layer to ensure environmental and mechanical stability without compromising weight and flexibility. The result was a device with a champion specific power of 44 W g−1 (average: 41 W g−1), an open circuit voltage of 1.15 V, and a championship efficiency of 20.1% (average: 18.1%) . To demonstrate scalability, a photovoltaic module consisting of 24 interconnected 1 cm2 solar cells was prepared and demonstrated energy-autonomous operation of a hybrid solar-powered quadcopter while accounting for only 1/400 of the weight of the drone. Demonstration of the performance and stability of ultralightweight perovskite solar cells highlights their potential as portable, cost-effective sustainable energy harvesting devices.

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• https://doi.org/10.1038/s41560-024-01500-2