Methylamine Gas Research Articles

Control of Methylamine Gas Treatment for Upscaling Perovskite Solar Module

Methylamine (MA0) gas treatment (MATM) is a process that involves the adsorption of MA0 on methylammonium (MA)‐based lead perovskite thin films, forming an adsorption intermediate, which appears as a visually transparent liquid. When MA0 is desorbed from this intermediate, recrystallization of the MA‐based perovskite occurs. Due to the highly reversible nature of MATM and its ability to inherently levelize the film surface through liquefaction, MATM is a promising method for fabricating uniform and intact perovskite thin films over large areas, which is crucial for the commercialization of perovskite solar cells. Herein, efforts to control the MATM process are presented, including slowing down the kinetics of MA adsorption by introducing a diluent into the MA stock solution, establishing a monitoring system to investigate the desorption process in detail, and demonstrating the success of MATM in fabricating perovskite solar modules. It is found that MATM not only heals morphological flaws but also promotes (110) orientation crystallinity and reduces trap density in recrystallized MAPbI3 films. Finally, MATM is applied to prepare perovskite minimodules using an in‐house designed MA‐induced liquefaction and recrystallization reactor. The minimodule (5 × 5 cm) fabricated using MATM achieves 18.32% efficiency, significantly surpassing the performance of those fabricated using antisolvent‐treating (7.50%) and vacuum drying (16.09%) methods.

Amine-releasable Mediator In situ Repair Perovskites for Efficient and Stable Perovskite Solar Cells.

Residual lead iodide (PbI2) is deemed to a double-edged sword in perovskite film as small amounts of PbI2 are beneficial to the photovoltaic performance, but excessive will cause degradation of photovoltaic performance and stability. Herein, an in situ repair strategy has been developed by introducing amine-releasable mediator (methylammonium pyridine-2-carboxylic, MAPyA) to eliminate over-residual PbI2 and regulate the crystal quality of perovskite film. Notably, MAPyA can be partially decomposed into methylamine (MA) gas and pyridine-2-carboxylic (PyA) during high temperature annealing. The released MA can locally form liquid intermediate phase, facilitating the reconstruction of perovskite microcrystals and residual PbI2. Moreover, the leftover PyA is confirmed to effectively passivate the uncoordinated lead ions in final perovskite film. Based upon this, superior perovskite film with optimized crystal structure and holistic negligible PbI2 is acquired. The assembled device realizes outstanding efficiency of 24.06 %, and exhibits a remarkable operational stability that maintaining 87 % of its origin efficiency after continuous illumination for 1480 h. And the unencapsulated MAPyA-treated devices present significant uplift in humidity stability (maintaining ~93 % of the initial efficiency over 1500 h, 50-60 % relative humidity). Furthermore, the further optimization of this strategy with nanoimprint technology proves its superiority in the amplificative preparation for perovskite films.

Amine‐releasable Mediator In situ Repair Perovskites for Efficient and Stable Perovskite Solar Cells

AbstractResidual lead iodide (PbI2) is deemed to a double‐edged sword in perovskite film as small amounts of PbI2 are beneficial to the photovoltaic performance, but excessive will cause degradation of photovoltaic performance and stability. Herein, an in situ repair strategy has been developed by introducing amine‐releasable mediator (methylammonium pyridine‐2‐carboxylic, MAPyA) to eliminate over‐residual PbI2 and regulate the crystal quality of perovskite film. Notably, MAPyA can be partially decomposed into methylamine (MA) gas and pyridine‐2‐carboxylic (PyA) during high temperature annealing. The released MA can locally form liquid intermediate phase, facilitating the reconstruction of perovskite microcrystals and residual PbI2. Moreover, the leftover PyA is confirmed to effectively passivate the uncoordinated lead ions in final perovskite film. Based upon this, superior perovskite film with optimized crystal structure and holistic negligible PbI2 is acquired. The assembled device realizes outstanding efficiency of 24.06 %, and exhibits a remarkable operational stability that maintaining 87 % of its origin efficiency after continuous illumination for 1480 h. And the unencapsulated MAPyA‐treated devices present significant uplift in humidity stability (maintaining ~93 % of the initial efficiency over 1500 h, 50–60 % relative humidity). Furthermore, the further optimization of this strategy with nanoimprint technology proves its superiority in the amplificative preparation for perovskite films.

Formation of perovskite by solid-gas reaction through low-temperature carbon counter electrode in hole-conductor-free perovskite solar cells

Recently, hole-conductor-free perovskite solar cells (PSCs) with carbon counter electrode (CCE) have attracted great attention for its high stability and low fabrication cost. Furthermore, it would lower the cost and simplify the manufacturing process of PSCs by low temperature processing instead of high temperature sintering for fabrication. In this case, however, it is very important to improve the interfacial contact between perovskite layer and CCE. In this work, we for the first time introduce solid-gas reaction between dimethylammonium lead iodide (DMAPbI3) in solid state under carbon layer and methylamine (MA) gas passed through CCE which is formed at low temperature of 120 ℃. Based on Brunauer-Emmett-Teller (BET) measurement and XRD analysis, it is found that MA gas can pass through our low-temperature CCE and perovskite crystals could be successfully formed by the reaction with DMAPbI3. In this case, due to the existence of liquid crystal intermediate state and volume expansion, interfacial contact would become better and the charge transfer and recombination characteristics have improved considerably. The best performance devices based on optimized MA gas treatment time exhibit higher efficiency of 12.4% than that of PSCs fabricated by conventional ways with low-temperature processed CCE (9.6%).

Amine Gas-Induced Reversible Optical Bleaching of Bismuth-Based Lead-Free Perovskite Thin Films.

Reversible optical property changes in lead-free perovskites have recently received great interest due to their potential applications in smart windows, sensors, data encryption, and various on-demand devices. However, it is challenging to achieve remarkable color changes in their thin films. Here, methylamine gas (CH3 NH2 , MA0 ) induced switchable optical bleaching of bismuth (Bi)-based perovskite films is demonstrated for the first time. By exposure to an MA0 atmosphere, the color of Cs2 AgBiBr6 (CABB) films changes from yellow to transparent, and the color of Cs3 Bi2 I9 (CBI) films changes from dark red to transparent. More interestingly, the underlying reason is found to be the interactions between MA0 and Bi3+ with the formation of an amorphous liquefied transparent intermediate phase, which is different from that of lead-based perovskite systems. Moreover, the generality of this approach is demonstrated with other amine gases, including ethylamine (C2 H5 NH2 , EA0 ) and butylamine (CH3 (CH2 )3 NH2 , BA0 ), and another compound, Cs3 Sb2 I9 , by observing a similar reversible optical bleaching phenomenon. The potential for the application of CABB and CBI films in switchable smart windows is investigated. This study provides valuable insights into the interactions between amine gases and lead-free perovskites, opening up new possibilities for high-efficiency optoelectronic and stimuli-responsive applications of these emerging Bi-based materials.

Perovskite grain fusion strategy via controlled methylamine gas release for efficient and stable formamide-based perovskite solar cells

The effectiveness of post-treatment on formamide (FA)-based perovskites by applying methylammonium (MA) has not been reported so far, due to the formation of fatal δ-phase. Herein, we select a series of carboxyl compounds to form their MA salts, utilizing the volatile nature of MA+, so as to control the release of MA gas via an MA-gas-releasing secondary grain growth (MGR-SGG) technique, stabilizing FA-based perovskite while inhibiting the formation of photo-inactive δ-phase. After such a treatment, perovskite grains fuse into larger ones, forming perovskites with better crystallinity, while the remaining compounds, including the carboxyl molecules and the undecomposed MA salts left on the perovskite surface, present passivation effect. The synergetic effects are tuned by varying the carboxyl acid backbones, and the moderate OPEM exhibits suitable MA gas release rate and strong interaction with perovskite, therefore sufficiently diminish defect density, contributing to increased open-circuit voltages by more than 20 mV, and enhanced maximum power conversion efficiency from 21.3% (untreated cells) to 22.4% (MGR-SGG treated cells), along with promoted device stability.

Methylamine‐Assisted Preparation of Ruddlesden‐Popper Perovskites for Stable Detection and Imaging of X‐Rays

AbstractSensitive and stable X‐ray detectors are essential for medical diagnostics, nondestructive industrial inspection, and security inspection. Halide perovskite X‐ray detectors are promising for direct X‐ray detection because of their high sensitivity and low limit of detection (LoD). However, their high and unstable dark current, caused by notorious ion migration in hybrid perovskites, limits their performance and long‐term operation stability. Moreover, it is still challenging to prepare high‐quality perovskite with millimeter‐thickness at a large‐scale. In this paper, solid–liquid transition of two‐dimensional (2D) Ruddlesden‐Popper (RP) perovskites enabled by methylamine gas (CH3NH2) is first reported. Based on this novel approach, dense RP perovskite films with tunable ion migration and superior electronic features are produced using a lamination process. The tradeoff between stability and detection performance of perovskite X‐ray detectors is successfully solved by tuning the quantum well width of RP perovskites. X‐ray detectors with a sensitivity of 5362.3 µC Gyair−1 cm−2, LoD of 8.1 nGyair s−1 and highly working stability are achieved simultaneously. Furthermore, single gamma photon detection is realized in the RP perovskite detectors, which further confirms their capability for detecting radiation at ultralow dose rates. This study paves the way for adopting polycrystalline RP perovskites in stable X‐ray detectors.

Kinetics, Products, and Brown Carbon Formation by Aqueous-Phase Reactions of Glycolaldehyde with Atmospheric Amines and Ammonium Sulfate.

Glycolaldehyde (GAld) is a C2 water-soluble aldehyde produced during the atmospheric oxidation of isoprene and many other species and is commonly found in cloudwater. Previous work has established that glycolaldehyde evaporates more readily from drying aerosol droplets containing ammonium sulfate (AS) than does glyoxal, methylglyoxal, or hydroxyacetone, which implies that it does not oligomerize as quickly as these other species. Here, we report NMR measurements of glycolaldehyde’s aqueous-phase reactions with AS, methylamine, and glycine. Reaction rate constants are smaller than those of respective glyoxal and methylglyoxal reactions in the pH range of 3–6. In follow-up cloud chamber experiments, deliquesced glycine and AS seed particles were found to take up glycolaldehyde and methylamine and form brown carbon. At very high relative humidity, these changes were more than 2 orders of magnitude faster than predicted by our bulk liquid NMR kinetics measurements, suggesting that reactions involving surface-active species at crowded air–water interfaces may play an important role. The high-resolution liquid chromatography–electrospray ionization–mass spectrometric analysis of filter extracts of unprocessed AS + GAld seed particles identified sugar-like C6 and C12 GAld oligomers, including proposed product 3-deoxyglucosone, with and without modification by reactions with ammonia to diimine and imidazole forms. Chamber exposure to methylamine gas, cloud processing, and simulated sunlight increased the incorporation of both ammonia and methylamine into oligomers. Many C4–C16 imidazole derivatives were detected in an extract of chamber-exposed aerosol along with a predominance of N-derivatized C6 and C12 glycolaldehyde oligomers, suggesting that GAld is capable of forming brown carbon SOA.

Self‐powered bifunctional perovskite photodetectors with both broadband and narrowband photoresponse

AbstractPhotodetectors generally operate exclusively in either the broadband or narrowband. Developing bifunctional photodetectors that can detect photons in both broadband and narrowband would bring significant versatility to the optoelectronic platform. Nevertheless, the design of bifunctional integrated devices remains challenging due to the differentiated strategies with respect to device structure and material combination. Herein, we propose introducing polyvinylpyrrolidone to increase the viscosity of the perovskite precursor solution, which introduces abundant defects and cavities into the perovskite film while maintaining a relatively low film thickness. Then, we use methylamine gas to postprocess the middle area of the film to promote directional recrystallization and densification, thereby realizing narrowband and broadband dual‐function photodetection in a single device at zero bias. Both ends of the film exhibit a near‐infrared peak response at 780 nm with a narrow full‐width at half maximum of approximately 30 nm without an external bias. The middle broadband photodetector exhibits a high responsivity of 329 mA W−1 and EQE up to 52.46% at 780 nm. We make full use of narrow‐band wavelength selective detection and broadband full‐spectrum detection to achieve double encryption during signal transmission. This work represents an important step toward the realization of perovskite‐based multifunctional integrated devices.image

Self-Powered Organometal Halide Perovskite Photodetector with Embedded Silver Nanowires.

Metal–semiconductor–metal (MSM) configuration of perovskite photodetectors (PPDs) suggests easy and low-cost manufacturing. However, the basic structures of MSM PPDs include vertical and lateral configurations, which require the use of expensive materials such as transparent conductive oxides or/and sophisticated fabrication techniques such as lithography. Integrating metallic nanowire-based electrodes into the perovskite photo-absorber layer to form one-half of the MSM PPD structure could potentially resolve the key issues of both configurations. Here, a manufacturing of solution-processed and self-powered MSM PPDs with embedded silver nanowire electrodes is demonstrated. The embedding of silver nanowire electrode into the perovskite layer is achieved by treating the silver nanowire/perovskite double layer with a methylamine gas vapor. The evaporated gold layer is used as the second electrode to form MSM PPDs. The prepared MSM PPDs show a photoresponsivity of 4 × 10−5 AW−1 in the UV region and 2 × 10−5 AW−1 in the visible region. On average, the devices exhibit a photocurrent of 1.1 × 10−6 A under white light (75 mW cm−2) illumination with an ON/OFF ratio of 83.4. The results presented in this work open up a new method for development and fabrication of simple, solution-processable MSM self-powered PPDs.

Methylamine gas healing of perovskite films: a short review and perspective

We summarize the internal chemical mechanism, crystallization kinetics and future prospects of the MA0 healing process.

Healing the Buried Cavities and Defects in Quasi-2D Perovskite Films by Self-Generated Methylamine Gas

Healing the Buried Cavities and Defects in Quasi-2D Perovskite Films by Self-Generated Methylamine Gas

Organic-Inorganic Perovskite Films and Efficient Planar Heterojunction Solar Cells by Magnetron Sputtering.

Organic–inorganic halide perovskites have been widely used in photovoltaic technologies. Despite tremendous progress in their efficiency and stability, perovskite solar cells (PSCs) are still facing the challenges of upscaling and stability for practical applications. As a mature film preparation technology, magnetron sputtering has been widely used to prepare metals, metallic oxides, and some semiconductor films, which has great application potential in the fabrication of PSCs. Here, a unique technology where high‐quality perovskite films are prepared via magnetron sputtering for controllable composition, solvent‐free, large‐area, and massive production, is presented. This strategy transforms the perovskite materials from powder to thin films by magnetron sputtering and post‐treatment (vapor‐assisted treatment with methanaminium iodide gas and methylamine gas treatment), which is greatly favorable to manufacture tandem solar cells. The power conversion efficiency (PCE) of PSCs with perovskite films fabricated by magnetron sputtering is 6.14%. After optimization, high‐performance perovskite films with excellent electronic properties are obtained and stable PSCs with excellent reproducibility are realized, showing a PCE of up to 15.22%. The entirely novel synthetic approach opens up a new and promising way to achieve high‐throughput magnetron sputtering for large‐area production in commercial applications of planar heterojunction and tandem PSCs.

An effective and reliable fluorescent sensor for selective detection of methylamine gas based on in-situ formation of MAPbBr3 perovskite nanocrystals in electrospun fibers

The development of fluorescent sensor based on lead-based perovskite nanomaterials is of the most intriguing for the design of quick check with low concentration. In the present work, a rapid, stable, and sensitive fluorescent sensor for selective detection of methylamine (MA) gas is firstly constructed based on in-situ formation of MAPbBr3 (methylamine lead bromide, that is CH3NH3PbBr3) perovskite nanocrystals (PNCs) in electrospun fibers by reacting MA gas with DMAPbBr3@PVDF (dimethylammonium lead bromide@poly (vinylidene fluoride), that is (CH3)2NH2PbBr3@PVDF) fibers. In this strategy, not only is the stability of PNCs significantly enhanced, but also does it retain the sensing efficiency due to the excellent permeability of the membrane. The sensor can maintain its stability after storage for two months due to its superior resistance to moisture, which is highly important for real-world applications. Finally, the nanofibers show a dual-mode sensor response to 5–200 ppm MA gas with a limit of detection (LOD) of 0.8 ppm.

Methylamine Gas Treatment Affords Improving Semitransparency, Efficiency, and Stability of CH3NH3PbBr3‐Based Perovskite Solar Cells

High bandgap semitransparent solar cells based on CH3NH3PbBr3 perovskites are attractive for building integration, tandem cells, and electrochemical applications. The lack of control of the CH3NH3PbBr3 perovskite growth limit the exploitation of CH3NH3PbBr3‐based perovskite solar cells. Herein, a post‐treatment is carried out after the initial CH3NH3PbBr3 crystallization based on methylamine gas that drastically enhances the perovskite quality leading to a highly crystalline film with improved average visible transmittance (AVT) close to 56%. Opaque devices showed outstanding results in terms of open‐circuit voltage and power conversion efficiency (PCE) reaching 1.54 V and 9.2%, respectively. These achievements are ascribed to a film with reduced morphological defects and better interface quality and reduced nonradiative pathways. For the first time, the fabrication of semitransparent CH3NH3PbBr3‐based solar cells is demonstrated reaching a maximum PCE equal to 7.6%, an AVT of the full stack device of 52%, and an excellent light stability at maximum‐power point tracking.

Methylamine gas treatment affords improving semi-transparency, efficiency and stability of CH3NH3PbBr3-based perovskite solar cells

Methylamine gas treatment affords improving semi-transparency, efficiency and stability of CH3NH3PbBr3-based perovskite solar cells

Rising from the Ashes: Gaseous Therapy for Robust and Large-Area Perovskite Solar Cells

Scalable fabrication of perovskite solar cells (PSCs) with high reliability is one of the most pivotal concerns that must be addressed before they get into the photovoltaic (PV) market. Scaling large-area high-quality perovskite films is of great importance in this process. Here, gaseous therapy has been proposed for the post-treatment of perovskite films with high scalability and low cost. An inspiring evolvement from poor perovskite films to high quality ones is demonstrated under a joint treatment of methylamine gas and hot solvent vapors. The perovskite films are completely reconstructed and repaired regardless of the morphology of the original films. As a consequence, small-area (0.09 cm2) and large-area (4 cm2) PSCs based on the healed MAPbI3 films can afford J-V scanned efficiencies of 19.2 and 16.5% under a reverse sweep, respectively. Furthermore, stabilized power outputs of 18.5 and 15.2% are obtained from the small one and large one under continuous maximum power point tracking.

Preparation of methylammonium lead iodide (CH3NH3PbI3) thin film perovskite solar cells by chemical vapor deposition using methylamine gas (CH3NH2) and hydrogen iodide gas

AbstractAn upscalable chemical vapor deposition setup has been built‐up and employed in producing methylammonium lead iodide (MAPI) thin film perovskite solar cells, leading to a maximum efficiency of 12.9%. The method makes use of methylamine gas and hydrogen iodide gas to transform a predeposited layer of lead(II)iodide (PbI2) into MAPI. Although the reaction mechanism includes the intermediate phases lead oxide (PbO) and lead hydroxide (Pb(OH)2), indicated at least on the surface of the samples by XPS, neither species could be observed in XRD measurements of the stepwise reaction, which show a mixture of highly oriented cubic and tetragonal MAPI perovskite lattice systems.

Fluorescence Turn-on and Wavelength-Shift Dual Response for Methylamine Gas Sensing Using HPbBr3/PbBr2@SiO2 Nanospheres

The defect-tolerant nature of lead halide perovskites renders high PLQYs by simply confining them in nanopores. In view of this character, a fluorescence turn-on and wavelength-shift dual responsive methylamine (MA) gas sensor is achieved using HPbBr3/PbBr2@SiO2 nanospheres (NSs). In this composite, the hydrophobic silica shell not only provides mesopores for the penetration of MA gas, but enhances the moisture stability of the MAPbBr3 perovskite nanocrystals generated after reacted with MA gas, improving the sensing performance. When exposed to the MA gas, the fluorescence is rapidly turned on due to the formation of MAPbBr3 perovskite nanocrystals. The enhanced photoluminescence is linearly with the MA concentration in the range of 0.08 – 6.3 μM with a LOD of 3.1 nM (S/N = 3). In addition, the photoluminescence peak is consistently red-shift from 478.7 nm to 510.6 nm when the MA concentration is increased from 0.083 to 6.3 µM. Correspondingly, the emission color is changed from weak blue to cyan, and to bright green, which imparts the potential for colorimetric sensing. By combining the turn-on and wavelength-guide sensing modes, this MA sensor is more flexible and the result is more reliable. Figure 1

Dual-Mode of Fluorescence Turn-On and Wavelength-Shift for Methylamine Gas Sensing Based on Space-Confined Growth of Methylammonium Lead Tribromide Perovskite Nanocrystals.

The defect-tolerant nature of lead halide perovskites renders outstanding luminescence by simple space-confined growth in nanopores. The fluorescence turn-on and wavelength-shift phenomena could be found in the formation of methylammonium lead tribromide (MAPbBr3) nanocrystals in hollow SiO2 nanospheres triggered by the reaction between methylamine (MA) gas and HPbBr3/PbBr2@SiO2 nanospheres. The enhanced fluorescence intensity is linear with the MA concentration in the range of 1.0-95 ppm with a limit of detection (LOD) of 70 ppb (S/N = 3). In addition, the maximum emission wavelength is consistently red-shifted from 478.7 to 510.6 nm as the MA concentration increases from 1.0 to 95 ppm, imparting the potential for colorimetric sensing. By combining the fluorescence turn-on and colorimetric sensing modes, the flexible method meets the demands for visual discrimination and point-of-care determination with portable devices.