Fabrication Of High-quality Perovskite Films Research Articles

Collaborative Fabrication of High-Quality Perovskite Films for Efficient Solar Modules through Solvent Engineering and Vacuum Flash System.

The vacuum flash solution method has gained widespread recognition in the preparation of perovskite thin films, laying the foundation for the industrialization of perovskite solar cells. However, the low volatility of dimethyl sulfoxide and its weak interaction with formamidine-based perovskites significantly hinder the preparation of cell modules and the further improvement of photovoltaic performance. In this study, we describe an efficient and reproducible method for preparing large-scale, highly uniform formamidinium lead triiodide (FAPbI3) perovskite films. This is achieved by accelerating the vacuum flash rate and leveraging the complex synergism. Specifically, we designed a dual pump system to accelerate the depressurization rate of the vacuum system and compared the quality of perovskite film formed at different depressurization rates. Further, to overcome the limitations posed by DMSO, we substituted N-methylpyrrolidone as the ligand solvent, creating a stable intermediate complex phase. After annealing, it can be transformed into a uniform and pinhole-free FAPbI3 film. Due to the superior quality of these films, the large area perovskite solar module achieved a power conversion efficiency of 22.7% with an active area of 21.4 cm2. Additionally, it obtained an official certified efficiency of 22.1% with an aperture area of 22 cm2, and it demonstrated long-term stability.

Materials chemistry for metal halide perovskite photovoltaics

Abstract Metal halide perovskite semiconductors are excellent materials for next-generation solar cells. As a result of research and development all over the world, the photoelectric conversion efficiency for single-cell devices has rapidly improved to over 26% (as of July 2023), while the record efficiency for silicon-on-perovskite tandem devices currently stands at 33.7% (reported in May 2023). Materials chemistry has made many important contributions toward these remarkable results. In this account, we will introduce our achievements in these areas of material chemistry research for improving the performance of perovskite photovoltaics, including the development of high-purity precursor materials, and precursor inks tailored for large-area printed perovskite films. Studies of the nucleation and crystallization process, including simulations, have led to the reliable fabrication of high-quality perovskite films. Diverse new charge collection materials, as well as compounds to effectively modify perovskite surfaces, have improved solar cell performance.

Additive Engineering of Imidazolium-based cation for defect passivation with enhanced performance and stability of carbon-based perovskite solar cells

Due to the rapid increase in the power conversion efficiency (PCE) of perovskite solar cells (PSCs) and approaching the theoretical maximum level in recent years, the main drawback of their future commercialization is to improve their long-term stability under existing environmental conditions. One of the problems with this technology lies in the absorbing layer, specifically the perovskite. In particular, when producing a perovskite film under ambient conditions, it is almost impossible to avoid film defects caused by environmental conditions (such as moisture, oxygen, and temperature), which could randomly change during the preparation process. Therefore, the fabrication of high-quality perovskite films is an urgent process that has a direct impact on the overall performance of the solar cells. The use of ionic liquids (ILs) as additives in perovskite precursor solutions is a promising strategy to improve not only the power conversion efficiency (PCE) but also the long-term stability of photovoltaic devices by controlling nucleation and crystal growth of perovskite film that avoids defects and produces high-quality perovskite layers. Here, the critical role of the ionic liquid 1-methyl-3-propylimidazolium iodide (1-MPII) in different perovskite precursor solutions such as MAPbI3 (I), MAPbI3-PbBr2 (B) and MAPbI3-PbCl2 (CL) on carbon-based perovskite solar cells (C–PSCs) under ambient conditions is extensively studied. The results show that 1-MPII ionic liquid activates the surface morphology of all perovskite films and improves solar cells’ efficiency due to the passivation of the uncoordinated Pb2+ defects. Furthermore, stability measurements show that the unencapsulated IL-modified devices for perovskites MAPbI3 (IIL), MAPbI3-PbBr2 (BIL), and MAPbI3-PbCl2 (CLIL) retained at 84 %, 86 %, and 80 % of their original PCE for over 1100 h under ambient conditions with 45 % relative humidity (RH), compared to the IL-free PSCs. Moreover, the IL-modified PSCs exhibited an increased electrical performance ranging from 16.5 % to 33 % depending on the type of perovskite it was used, so that long-term stability also was reinforced.

Ion-exchange-induced slow crystallization of 2D-3D perovskite thick junctions for X-ray detection and imaging

<h2>Summary</h2> Metal-halide perovskites have recently emerged as promising candidates for next-generation X-ray detectors, mainly benefiting from their low-temperature solution processability, chemical versatility, low cost, and excellent and tunable optoelectronic properties. However, the fabrication of perovskite thick junctions is very challenging, particularly for solution-processed thick photodiodes. Here, we report an ion-exchange strategy to prepare two-dimensional (2D)-3D perovskite thick films for directly detecting X-rays. This approach provides a facile and generic fabrication of high-quality perovskite films with various perovskite precursors, achieving uniform morphology, tunable thickness, and vertically monolithic crystal phase. The dynamic processes of the ion exchange were fully characterized and studied with multiple <i>in situ</i> and <i>ex situ</i> techniques, e.g., photoluminescence spectroscopy and X-ray diffraction. After optimization, record-high X-ray sensitivity of 1.36 × 10⁴ μC Gy_air^-1 cm^-2 and ultra-low detection limit of 4.2 nGy_air s^-1 were achieved based on the optimized (BA₂PbBr₄)_0.5FAPbI₃ detectors, demonstrated along with 32 × 32 pixel prototypical photodetector arrays.

All-Inorganic Perovskite Solar Cells: Recent Advancements and Challenges.

Organic–inorganic metal-halide-based hybrid perovskite solar cells (SCs) have attracted a great deal of attention from researchers around the globe with their certified power conversion efficiencies (PCEs) having now increased to 25.2%. Nevertheless, organic–inorganic hybrid halide perovskite SCs suffer the serious drawback of instability with respect to moisture and heat. However, all-inorganic perovskite SCs have emerged as promising candidates to tackle the thermal instability problem. Since the introduction of all-inorganic perovskite materials to the field of perovskite photovoltaics in 2014, a plethora of research articles has been published focusing on this research topic. The PCE of all-inorganic PSCs has climbed to a record 18.4% and research is underway to enhance this. In this review, I survey the gradual progress of all-inorganic perovskites, their material design, the fabrication of high-quality perovskite films, energetics, major challenges and schemes opening new horizons toward commercialization. Furthermore, techniques to stabilize cubically phased low-bandgap inorganic perovskites are highlighted, as this is an indispensable requirement for stable and highly efficient SCs. In addition, I explain the various energy loss mechanisms at the interface and in the bulk of perovskite and charge-selective layers, and recap previously published reports on the curtailment of charge-carrier recombination losses.

Solvent Free Laminated Fabrication of Lead Halide Perovskites for Sensitive and Stable X-ray Detection.

The halide perovskite X-ray detector can meet the urgent needs of low-dose medical imaging by X-rays. However, there is still a pressing challenge in lacking robust methods for large-scale fabrication of high-quality perovskite films with tunable thickness. Here we report a laminated fabrication of polycrystalline MAPbI3 by using solvent-free liquid perovskite molten-salt (PMS), that offers reduced toxic issue, scalable fabrication, and highly tunability in film thickness. Nylon membrane was chosen as a scaffold for the infiltration of PMS, which simultaneously acts as a physical barrier to suppress the ionic migration in the MAPbI3-nylon composite (denoted as MAPbI3-LLP). The enhanced material properties result in good stability and high performance of X-ray detectors that show low detection limit and high sensitivity. Additionally, single gamma-ray photon detection was realized by MAPbI3-LLP detectors. The promising performance characteristics of such polycrystalline detectors can accelerate the adoption of polycrystalline perovskites in X-ray imaging and gamma-ray detection.

Flexible Perovskite Solar Cells: Progress and Prospects

Flexible perovskite solar cells (FPSCs) have shown great potential in the field of wearable power supply and integration with architectures in the future due to their advantages of high flexibility, light weight, portability, and compatibility with irregular electronic products. As a promising photovoltaic technology compatible with roll-to-roll manufacturing process, FPSCs have made significant progress in the past several years through composition engineering, interface modification, optimization of fabrication process, and exploitation of new charge transport materials. As a result, the light-to-electricity power conversion efficiency of FPSCs has exceeded 20% recently. In this mini review, the latest developments of FPSCs are systematically summarized and discussed, including the flexible substrates and electrodes, as well as the fabrication of high-quality perovskite films. Finally, a prospect on the massive manufacturing of FPSCs as well as the challenge is also discussed.

Impact of halide additives on green antisolvent and high-humidity processed perovskite solar cells

Organometal halide perovskites have recently gained remarkable interest as a light absorber for photovoltaic technology. However, the majority of efficient perovskite solar cells (PSCs) are fabricated in the glovebox. From the mass production perspective, it is vital to improve the quality of ambient-processed perovskite, as well as to reduce health risks, costs, and complexity of fabrication. This study investigates the effect of using green antisolvent ethyl acetate with various halide additives on the performance of ambient-processed planar PSCs by a one-step deposition method, under a high relative humidity (RH) of 50–60%. Differences in microstructures, crystallinity, surface chemistry and optoelectronic properties for the green antisolvent and ambient-processed perovskite films with the addition of PbCl2, PbBr2, and MAI are observed, compared to the pristine film. Ambient-processed perovskite films with PbCl2 addition remarkably improves the PCE of the pristine device by 17.3% and achieves a fill factor up to 76.3%. Addition of PbCl2 also enhances the stability of the devices and retains 81% of their initial PCEs after storage in ambient air for 28 days. These findings provide a strategy of using halide additives and green antisolvent for the fabrication of high-quality perovskite films under high relative humidity without the need of glovebox.

Atmosphere dependent gas-solid reaction for high-quality MAPbBr3 perovskite solar cells

It is imperative to develop a high-quality hybrid perovskite film with large crystallinity and smooth morphology for high-performance stable perovskite solar cells. Herein, vapor assisted crystallization method was used to fabricate crystalline CH3NH3PbBr3 (MAPbBr3) films through the precisely controlled gas-solid reaction. The effect of different atmosphere condition (N2, vacuum and air conditions) on the final MAPbBr3 films was investigated. It is found that the N2 atmosphere is in favor for obtaining uniform perovskite film (MAPbBr3-N2) which exhibits good crystallization, strong absorption and few defects due to the slow crystallization reaction. In this way, the MAPbBr3-N2-based device shows an open-circuit voltage (Voc) of 1.20 V and power conversion efficiency (PCE) of 4.88%, much higher than the devices fabricated in the vacuum state. Based on this atmosphere, a champion PCE of 7.30% with a Voc of 1.384 V can be achieved by introducing mesoporous TiO2 layer. Our results could provide valuable information for the fabrication of high-quality perovskite films for photoelectric device.

Recent progress in perovskite solar cells: the perovskite layer.

Perovskite solar cells (PSCs) are set to be game changing components in next-generation photovoltaic technology due to their high efficiency and low cost. In this article, recent progress in the development of perovskite layers, which are the basis of PSCs, is reviewed. Achievements in the fabrication of high-quality perovskite films by various methods and techniques are introduced. The reported works demonstrate that the power conversion efficiency of the perovskite layers depends largely on their morphology and the crystalline quality. Furthermore, recent achievements concerning the scalability of perovskite films are presented. These developments aim at manufacturing large-scale perovskite solar modules at high speed. Moreover, it is shown that the development of low-dimensional perovskites plays an important role in improving the long-term ambient stability of PSCs. Finally, these latest advancements can enhance the competitiveness of PSCs in photovoltaics, paving the way for their commercialization. In the closing section of this review, some future critical challenges are outlined, and the prospect of commercialization of PSCs is presented.

Pre-crystallisation applied in sequential deposition approaches to improve the photovoltaic performance of perovskite solar cells

Abstract The fabrication process for perovskite films is critical for their microstructure and photo-electrical properties. In this study, a pre-preparation step for perovskite crystal particles with a conventional two step spin-coating method was introduced for improving the quality of the prepared perovskite films. By adding CH3NH3I into the PbI2 precursor solution and performing anti-solvent extraction during the preparation process, a small amount of perovskite crystal particles was produced in the PbI2 layers. We demonstrated that the pre-preparation of perovskite crystal particles enhanced the grain size and coverage of the perovskite films due to modification of the surface morphology and crystallisation of the PbI2 layers. Furthermore, after optimisation, the crystal size in the perovskite films reached almost 3 μm, which tremendously enhanced the generation and transportation of photo-generated carriers in photo-voltaic devices. Under illumination, the fill factor (FF) and short circuit current density (Jsc) of the corresponding devices increased, and the photoelectric conversion efficiency (PCE) was enhanced from 11.7% to 17.5%. Further, the stability of the devices in dark humid air was improved. Our results demonstrate that pre-preparing the perovskite crystal particles is useful for the fabrication of high-quality perovskite films. This approach can also be applied to devices based on perovskite films with other compositions.

Ethylenediamine chlorides additive assisting formation of high-quality formamidinium-caesium perovskite film with low trap density for efficient solar cells

Dual-cation formamidinium-caesium (FACs) perovskite shows good thermal stability, but a great number of trap states existing in the FACs perovskite film impair its photoelectric conversion efficiency and long-term stability. In this work, ethylenediamine chlorides (EDACl2), a new type Lewis base trap deactivator, is synthesized and then applied to the perovskite precursor solution to assist the formation of FACs perovskite film with less trap states. A series of photoelectric measurements reveal that the charge transport of FACs perovskite film, mediated by EDACl2 additive, is promoted and the non-radiative recombination process is reduced as well. By optimizing the EDACl2 additive amount and Br composition, the EDACl2-engineered perovskite solar cells (PSCs) with structures of ITO/SnO2/Cs0.15FA0.85PbI2.7Br0.3/Spiro-MeOTAD/Ag and ITO/SnO2/Cs0.15FA0.85PbI2.7 Br0.3/carbon, achieve their respective champion efficiencies of 19.68% and 15.56%, along with negligible hysteresis. Particularly, the carbon-based FACs device with EDACl2 exhibits good air-, thermal- and photostability. This work provides a facile and efficient ion additive engineering for fabrication of high-quality perovskite films and high-performance PSCs.

Additives in metal halide perovskite films and their applications in solar cells

Abstract The booming growth of organic-inorganic hybrid lead halide perovskite solar cells have made this promising photovoltaic technology to leap towards commercialization. One of the most important issues for the evolution from research to practical application of this technology is to achieve high-throughput manufacturing of large-scale perovskite solar modules. In particular, realization of scalable fabrication of large-area perovskite films is one of the essential steps. During the past ten years, a great number of approaches have been developed to deposit high quality perovskite films, to which additives are introduced during the fabrication process of perovskite layers in terms of the perovskite grain growth control, defect reduction, stability enhancement, etc. Herein, we first review the recent progress on additives during the fabrication of large area perovskite films for large scale perovskite solar cells and modules. We then focus on a comprehensive and in-depth understanding of the roles of additives for perovskite grain growth control, defects reduction, and stability enhancement. Further advancement of the scalable fabrication of high-quality perovskite films and solar cells using additives to further develop large area, stable perovskite solar cells are discussed.

Efficient inverted all inorganic CsPbI3 planar solar cells via twice-coating in air condition

Recently, solar cells based on inorganic cesium lead triiodide perovskite materials have received considerable attention. However, the quality and thickness of perovskite films are still out from satisfaction due to the limited solubility of the precursor materials. Here, a simple twice-coating process is reported for fabrication of high-quality perovskite films in a complete air condition. Defects such as pinholes, can be effectively eliminated by the second coating with further growth of the grain sizes, thus greatly suppressing charge recombination in these perovskite films. Furthermore, the improved film thickness can ameliorate the absorption of incident light. In consequence, the power conversion efficiency of 11.05% with comprehensively improved device parameters is obtained in traditional inverted planar perovskite solar cells, with a dramatic increase of 42% being compared with the control device (7.83%). In addition, the device's stability is also improved due to such high quality twice-coated perovskite films. The results reveal that such twice-coating technique is a promising choice for high-stablilty and efficient perovskite solar cells.

A Review of the Role of Solvents in Formation of High-Quality Solution-Processed Perovskite Films.

Recently, perovskite solar cells have attracted great attention because of their outstanding photovoltaic performance and ease of fabrication. High-quality perovskite films hold a key in getting highly efficient perovskite solar cells. Solution-processed fabrication technique is the most widely adopted for preparing perovskite films because of its low cost. In the solution-proceed perovskite films, solvents not only play the role of dissolving the solute but also participate in the crystallization of perovskite. In the one-step method, solvents play key roles in controlling morphology, widening process window, and achieving room-temperature crystallization of perovskite films. In addition, the solvents play important roles in controlling the nuclei/growth, suppressing volume expansion during the two-step method. Especially, the solvent can induce grain coarsening during the annealing process. A deep understanding of the multiplicity of roles during the formation of perovskite films will help understand the formation mechanism of perovskite films. Here, a systematic review on the progress in fabrication of high-quality perovskite films by making use of solvent to control the crystallization is presented. Meanwhile, we elucidate the key roles of solvent in the fabrication of high-quality perovskite films.

Br-containing alkyl ammonium salt-enabled scalable fabrication of high-quality perovskite films for efficient and stable perovskite modules

The incorporation of a Br-containing tetrabutylammonium salt into perovskite precursors demonstrates superior advantages in both crystallization and large-area uniformity control during the scalable blade-coating of perovskite films.

Effect of bidentate and tridentate additives on the photovoltaic performance and stability of perovskite solar cells

Fabrication of high-quality perovskite films with a large grain size and fewer defects is always crucial to achieve efficient and stable perovskite solar cells (PSCs).

A mixed solvent for rapid fabrication of large-area methylammonium lead iodide layers by one-step coating at room temperature

A new mixed solvent enables rapid fabrication of high-quality perovskite films directly by one-step spin-coating or blade-coating.

Morphology Engineering: A Route to Highly Reproducible and High Efficiency Perovskite Solar Cells.

Despite the rapid increase in the performance of perovskite solar cells (PSC), they still suffer from low lab-to-lab or people-to-people reproducibility. Aiming for a universal condition to high-performance devices, we investigated the morphology evolution of a composite perovskite by tuning annealing temperature and precursor concentration of the perovskite film. Here, we introduce thermal annealing as a powerful tool to generate a well-controlled excess of PbI2 in the perovskite formulation and show that this benefits the photovoltaic performance. We demonstrated the correlation between the film microstructure and electronic property and device performance. An optimized average grain size/thickness aspect ratio of the perovskite crystallite is identified, which brings about a highly reproducible power conversion efficiency (PCE) of 19.5 %, with a certified value of 19.08 %. Negligible hysteresis and outstanding morphology stability are observed with these devices. These findings lay the foundation for further boosting the PCE of PSC and can be very instructive for fabrication of high-quality perovskite films for a variety of applications, such as light-emitting diodes, field-effect transistors, and photodetectors.

Identifying the Molecular Structures of Intermediates for Optimizing the Fabrication of High-Quality Perovskite Films.

During the past two years, the introduction of DMSO has revolutionized the fabrication of high-quality pervoskite MAPbI3 (MA = CH3NH3) films for solar cell applications. In the developed DMSO process, the formation of (MA)2Pb3I8·2DMSO (shorted as Pb3I8) has well recognized as a critical factor to prepare high-quality pervoskite films and thus accomplish excellent performances in perovskite solar cells. However, Pb3I8 is an I-deficient intermediate and must further react with methylammonium iodide (MAI) to be fully converted into MAPbI3. By capturing and solving the molecular structures of several intermediates involved in the fabrication of perovskite films, we report in this work that the importance of DMSO is NOT due to the formation of Pb3I8. The use of different PbI2-DMSO ratios leads to two different structures of PbI2-DMSO precursors (PbI2·DMSO and PbI2·2DMSO), thus dramatically influencing the quality of fabricated perovskite films. However, such an influence can be minimized when the PbI2-DMSO precursor films are thermally treated to create mesoporous PbI2 films before reacting with MAI. Such a development makes the fabrication of high-quality pervoskite films highly reproducible without the need to precisely control the PbI2:DMSO ratio. Moreover, the formation of ionic compound (MA)4PbI6 is observed when excess MAI is used in the preparation of perovskite film. This I-rich phase heavily induces the hysteresis in PSCs, but is readily removed by isopropanol treatment. On the basis of all these findings, we develop a new effective protocol to fabricate high-performance PSCs. In the new protocol, high-quality perovskite films are prepared by simply treating the mesoporous PbI2 films (made from PbI2-DMSO precursors) with an isopropanol solution of MAI, followed by isopropanol washing. The best efficiency of fabricated MAPbI3 PSCs is up to 19.0%. As compared to the previously reported DMSO method, the devices fabricated by the method reported in this work display narrow efficiency distributions in both forward and reverse scans. And the efficiency difference between forward and reverse scans is much smaller.