Anti-solvent Assisted Crystallization Research Articles

Hydrochromic convertibility on fiberized self-assembling of copper-based perovskite quantum dots

Halide perovskite presents great competitive advantages in the new generation of stimuli-responsive materials, while the tuning of fluorescence emission is still limited by irritative factors and external conditions. Herein, anti-solvent assisted crystallization and in-situ synthesis are innovatively combined to accomplish the fiberized self-assembly of copper-based perovskite quantum dots economically and environmentally, which makes humidity a novel stimulus for luminescence regulation. Under the excitation of medium-wave UV, the original Cs3Cu2I5-CsCu2I3@polyacrylonitrile (CCI@PAN) fibers exhibit a main emission peak of 460 nm with a shoulder at 550 nm, and the intensity of shoulder peak is gradually increased with the continuous addition of moisture. Switching from blue to yellow fluorescence is achieved in CCI@PAN fiber membrane by the introduction of water, which is attributed to the ultra-high solubility of CsI in water. Moreover, owing to the spatial limitation of the nanofibers, the unique incomplete reversibility exhibited by the nanofiber membrane during water removal predicts that the nanofiber membrane can be used as a permanent recording material. Overall, this work deeply explores the influence of humidity on the fluorescence and structure of perovskite quantum dots, providing a method to synthesize innovative perovskite nanofiber composites based on emission conversion, which has broad prospects in advanced anti-counterfeiting, biological protection display, information encryption and smart wearable devices.

Fabrication and Characterization of a Lead-Free Cesium Bismuth Iodide Perovskite through Antisolvent-Assisted Crystallization.

Cesium bismuth iodide perovskite material offers good stability toward ambient conditions and has potential optoelectronic characteristics. However, wide bandgap, absorber surface roughness, and poor surface coverage with pinholes are among the key impediments to its adoption as a photovoltaic absorber material. Herein, bandgap modification and the tailoring of surface morphology have been performed through molar ratio variation and antisolvent treatment, whereby type III antisolvent (toluene) based on Hansen space has been utilized. XRD and Raman spectroscopy analyses confirm the formation of a 0D/2D mixed dimensional structure with improved optoelectronic properties when the molar ratio of CsI/BiI3 was adjusted from 1.5:1 to 1:1.5. The absorption results and Tauc plot determination show that the fabricated film has a lower bandgap of 1.80 eV. TRPL analysis reveals that the film possesses a very low charge carrier lifetime of 0.94 ns, suggesting deep defects. Toluene improves the charge carrier lifetime to 1.89 ns. The average grain size also increases from 323.26 nm to 444.3 nm upon toluene addition. Additionally, the inclusion of toluene results in a modest improvement in PCE, from 0.23% to 0.33%.

Unlocking the potential of antisolvent-free perovskite solar cells: Modulating crystallization and intermediates through a binary volatile additive strategy

High-quality perovskite polycrystalline thin films are generally achieved through antisolvent-assisted crystallization, a crucial process that facilitates desolvation. However, antisolvent method is limited by issues of toxicity and fabrication complexity. Here, we introduce a “binary volatile additive” strategy using methylammonium chloride (MACl) and trifluoroacetamide (TFAA) in dimethylformamide/N-methyl-2-pyrrolidone co-solvent system, enabling end-to-end management of antisolvent-free crystallization process. Combining in-situ characterizations and DFT calculations, we prove that TFAA adjusts coordination with perovskite intermediates, facilitating solvent removal and promoting the formation of nuclei, while MACl reduces the formation energy of α-phase formamidinium-based perovskite. Moreover, TFAA not only releases the residual strain caused by MACl, but also in combination with MACl, synergistically widens crystallization window and regulates ripening process, allowing for precise fabrication of homogeneous perovskite films with suppressed defects. By employing the “binary volatile additive” approach, we achieve perovskite solar cells with a power conversion efficiency up to 22.4% and elongated storage life (93% PCE retention over 1000 hours). Our study offers a simple and sustainable approach to produce high-quality perovskite films without the acquisition of antisolvent, streamlining the fabrication process.

Antisolvent Engineering to Enhance Photovoltaic Performance of Methylammonium Bismuth Iodide Solar Cells

High absorption ability and direct bandgap makes lead-based perovskite to acquire high photovoltaic performance. However, lead content in perovskite becomes a double-blade for counterbalancing photovoltaic performance and sustainability. Herein, we develop a methylammonium bismuth iodide (MBI), a perovskite-derivative, to serve as a lead-free light absorber layer. Owing to the short carrier diffusion length of MBI, its film quality is a predominant factor to photovoltaic performance. Several candidates of non-polar solvent are discussed in aspect of their dipole moment and boiling point to reveal the effects of anti-solvent assisted crystallization. Through anti-solvent engineering of toluene, the morphology, crystallinity, and element distribution of MBI films are improved compared with those without toluene treatment. The improved morphology and crystallinity of MBI films promote photovoltaic performance over 3.2 times compared with the one without toluene treatment. The photovoltaic device can achieve 0.26% with minor hysteresis effect, whose hysteresis index reduces from 0.374 to 0.169. This study guides a feasible path for developing MBI photovoltaics.

Photovoltaic Performance Improvement of All‐Inorganic CsPbBr3 Perovskite Solar Cells by Antisolvent Assisted Crystallization

AbstractAll‐inorganic CsPbBr3 perovskite solar cells (PSCs) are expected to form semitransparent or top‐cell of tandem solar cells with Cu(In,Ga)Se2 or crystalline silicon solar cells owing to their outstanding environmental tolerance and wide bandgap. However, the commonly solution‐processed CsPbBr3 perovskite films usually suffer from inferior film quality. Herein, we propose antisolvent assisted crystallization method to prepare CsPbBr3 films by multi‐step spin‐coating process. During the spin‐coating step, the underlying PbBr2 layer is treated with anisole antisolvent in different amount of 0, 50, 100, 150, and 200 μl, respectively, and heated at 80 °C for 30 min. Thus, CsPbBr3 films with high crystallinity, less grain boundaries and good coverage are prepared. The champion power conversion efficiency (PCE) of devices based on antisolvent treatment reaches 6.5 %, compared to that of devices without antisolvent treatment (PCE 4.97 %). Moreover, the devices treated with antisolvent without encapsulation exhibit good stability under ambient conditions. The antisolvent assisted crystallization provides an effective route for improving the quality of CsPbBr3 films and promotes the commercialization of all‐inorganic CsPbBr3 PSCs.

Low-temperature synthesis of stable blue Cesium lead bromide perovskite nanoplates with high quantum efficiency for display applications

Despite heavy research, the efficiencies of blue perovskite light-emitting diodes (LEDs) lag behind those of their green and red cousins. One of the most critical problems is the lack of technology to obtain both high blue emission and spectral stability of perovskite in thin films. Herein, we employ low-temperature synthesis of CsPbBr3 nanoplates (NPLs) by anti-solvent assisted crystallization method using green ethylacetate anti-solvent, which show high absolute photoluminescence quantum yield (PLQY = 90.2%), blue emission at 464 nm with a narrow emission line width (15 nm), small Stokes shift (5 nm) and the average PL decay lifetime (6.91 ns). Significantly, there is no obvious QY loss at different storage conditions. Furthermore, the PL can be tuned from blue to green (457–513 nm) by controlling the amount of precursor injected into anti-solvent. For the first time, we utilize all-bromide-based inorganic perovskites to fabricate ultraviolet-pumped white LEDs (UV-WLEDs) and optimize the chromaticity coordinate of WLEDs, whose CIE color temperature (CCT) is 6083 K. Finally, highly efficient blue LED device using CsPbBr3 nanoplates (464 nm) with high external quantum efficiency (EQE) of 2.03% was fabricated and spectral stability of CsPbBr3 nanoplates under constant current density was demonstrated. This work will be expected to facilitate the development of the blue light source for WLEDs and displays.

Anti-solvent engineering via potassium bromide additive for highly efficient and stable perovskite solar cells

Anti-solvent assisted crystallization is commonly employed method to achieve high-quality perovskites attributed to its great operability. Herein, we report an anti-solvent engineering approach via simply using potassium bromide (KBr) additive with commonly used chlorobenzene (CB) in triple-cation perovskite solar cells (PSCs). We show that the KBr additive in the CB anti-solvent not only increases the crystallinity and passivates the perovskite top surface defects, but also leads to suppressed nonradiative recombination and facilitates charge extraction at interfaces. Interestingly, due to the halide vacancies filling with K + ions, hysteresis behavior in the treated perovskite layer was suppressed. Consequently, a champion power conversion efficiency (PCE) of 18.29% was yielded for anti-solvent engineering employing KBr (an 20% improvement in PCE compared to the CB-only anti-solvent device). Furthermore, the optimized device based on KBr demonstrated improved stability, maintaining 80% of its original efficiency after aging in an environment with a relative humidity of 30–50% for 1080 h. Our study reports the significant role of anti-solvent engineering in improving perovskite's quality for efficient PSCs and develops the potential for PSC commercialization. • KBr additive is used to modify the perovskite layer in perovskite solar cells. • The KBr treatment of perovskite leads to an improvement of carrier extraction. • A high- PCE of 17.39% is achieved.

A self-powered β-Ga2O3/CsCu2I3 heterojunction photodiode responding to deep ultraviolet irradiation

In this paper, a lead-free halide perovskite CsCu2I3 film with high stability was prepared by the anti-solvent assisted crystallization method. Then, we coupled it with Ga2O3 to prepare a corresponding heterojunction deep ultraviolet (UV) photodetector. After testing, we concluded that the photodetector is sensitive to 254 nm UV light. The photodetector has good reproducibility, and has an ultra-high photo-to-dark current ratio (PDCR) of more than 105. In addition, under a bias of 10 V and an illuminated intensity of 200 μW/cm2, the responsivity (R) and specific detectivity (D*) reached 20 mA/W and 107 cm Hz1/2 W−1 (Jones), and the external quantum efficiency (EQE) is 10%. Meanwhile, the prepared photodetector could operate at zero bias, i.e., self-powered operation, along with a photocurrent of about 1 nA under illumination with UV light intensity of 200 μW/cm2.

Phase control in the synthesis of cesium copper iodide compounds for their photoluminescence and radioluminescence study

Lead-free metal halide perovskites have attracted much attention owing to their non-toxicity and excellent optical properties. Especially, cesium copper iodide compounds exhibit advantages of good environmental stability and low cost, rendering promising potential applications in optoelectronic devices field. Here, we use an anti-solvent assisted crystallization method to realize phase control syntheses of CsCu2I3 and Cs3Cu2I5 by varying the concentrations of precursor solution. Using high precursor solution concentrations, Cs3Cu2I5 with strong blue emission peak at 440 nm is prepared. While the CsCu2I3 is fabricated at low precursor solution concentrations, with the yellow emission peak of 580 nm. Furthermore, the UV-pumped light-emitting diodes (UV-LEDs) are realized by adopting CsCu2I3 and Cs3Cu2I5 powders as phosphors, and we also obverse the scintillation characteristic of the cesium copper iodide powders, showing potential applications for lighting and X-ray detection devices.

Surface Modification of Cs0.1(CH3NH3)0.9PbI3 by Isopropanol as Green Antisolvent for Efficiency Enhancement of Perovskite Solar Cells

Surface modification of Cs0.1(CH3NH3)0.9PbI3 is investigated by antisolvent‐assisted crystallization (ASAC). The perovskite solar cells (PSCs) of FTO/SnO2/Cs0.1(CH3NH3)0.9PbI3/spiro‐OMeTAD/Ag are also fabricated. It is found that isopropanol‐treated devices exhibit a power conversion efficiency (PCE) of 16.3%, which is higher than chlorobenzene‐ (11.5%) and toluene‐treated devices (12.8%). The efficiency enhancement by isopropanol treatment can be attributed to better surface coverage, larger grain size, and less pinholes confirmed by scanning electron microscopy (SEM) and X‐rays diffraction (XRD) results, indicating an increase in short‐circuit current density (Jsc). In addition, the increase in open‐circuit voltage (Voc) can be confirmed by photoluminescence (PL) spectra, which can be suggested to the reduce the nonradiative recombination loss in the isopropanol‐treated film. The wettability of perovskite films is studied by contact angle measurement, resulting in a higher hydrophobic surface from isopropanol‐treated devices. Also, the charge dynamic behavior of PSC devices is investigated by open‐circuit voltage decay (OCVD) measurement. It is found that the charge carrier lifetime of the isopropanol‐treated device is longer than that of chlorobenzene and toluene. Therefore, surface modification of perovskite by isopropanol treatment can enhance efficiency and isopropanol can be used as an alternative green antisolvent for the perovskite process.

Green solvent engineering for environment-friendly fabrication of high-performance perovskite solar cells

Antisolvent-assisted crystallization is a common process to fabricate high-performance perovskite solar cells (PSCs). At present, toxic organic solvents such as toluene or chlorobenzene have been used as typical antisolvents to fabricate compact perovskite absorber layer for a device, but their impact to environment or human/animal health has remained a challenge to be resolved for commercialization of PSCs. In this study, we suggest (R)-(+)-limonene and 2-methyltetrahydrofuran as eco-compatible and less-toxic antisolvents for preparing high-quality perovskite absorber layer in the inverted PSCs. The green antisolvents afford smooth, compact, less-defect, and full coverage perovskite films, comparable to the typical halogenated antisolvent-processed perovskite films, delivering a PCE up to 18.04% in CH3NH3PbI3-based device. The green antisolvent also demonstrated promising PCEs of 17.85%, 13.46%, and 10.04% in CH3NH3PbI3, CsPbI2Br, and BA2MA3Pb4I13-based PSCs accompanied with a halogen-free solvent-processed PC61BM layer. This work demonstrates a great potential of green antisolvents as a universal approach in obtaining high-quality perovskite films for fabricating high-efficiency PSCs.

Green antisolvent additive engineering to improve the performance of perovskite solar cells

High-quality perovskite films with larger grain size and fewer defects is a prerequisite for high-performance perovskite solar cells (PSCs). Antisolvent-assisted crystallization is an effective approach to obtain compact and uniform perovskite films; however, the majority of antisolvents currently applied have strong toxicity, and the control of perovskite crystallization is not easy through single antisolvent. In this work, a green antisolvent of ethyl acetate (EA) with acetylacetone (AA) additive is used to fine-tune perovskite crystallization and passivate defect, which produces uniform and compact CH3NH3PbI3 perovskite films having larger grain and fewer grain boundaries and reduced defect density. Meanwhile, the interfacial hydrophobic characteristic of the perovskite films is enhanced. At the optimized concentration of AA in EA, the power conversion efficiency (PCE) of the CH3NH3PbI3 PSCs was improved from 19.2% to 21.1% and their stability in air was also enhanced. These results present a green antisolvent additive engineering strategy to enhance the crystallinity, passivate defects, and fabricate efficient and stable PSCs.

A facile green solvent engineering for up-scaling perovskite solar cell modules

Organic-inorganic hybrid halide perovskite solar cells (PSCs) have shown the potential for the commercialization due to its high efficiency and low cost. How to scale up the module nowadays becomes a great challenge. Anti-solvent assisted crystallization is one of the most widely used methods to obtain pinhole-free homogeneous perovskite films owing to its advantage of low cost and simple process. The commonly used anti-solvents are toxic, such as chlorobenzene and toluene. Herein, we have made an effort to find a green solvent engineering by the anti-solvent bath to produce large area uniform perovskite films. Compared to the traditional solvent processed perovskite films, the films produced by n-butyl alcohol soaking exhibit smoother surface and superior performance. A moderate concentration of FAI/MABr has been added in the n-butyl alcohol solution to compensate for the loss of FAI/MABr during the soaking step. By this means, it alleviates the phenomenon of cracks on the perovskite surface, which exhibited a champion efficiency of 17.67% for PSCs with small area of 0.16 cm2 and a PCE of 13.85% for 10 cm × 10 cm perovskite solar modules.

Regulated perovskite crystallinity via green mixed antisolvent for efficient perovskite solar cells

Abstract Organometallic halide perovskite absorption layer with excellent surface morphology and large grain size is very important for fabricating efficient perovskite solar cells (PSCs). The antisolvent assisted crystallization (ASAC) has been proved to be an effective tactic to prepare compact and uniform polycrystalline perovskite film. However, most of the antisolvents currently used are highly toxic, and the perovskite crystallization process is difficult to control using pure antisolvent. Here, a green strategy is developed to improve the nucleation kinetics of perovskite precursor and the perovskite crystallization process. A mixed green antisolvent of ethyl acetate (EA)/petroleum ether (PE) is employed to regulate the crystallization of perovskite and replace traditional chlorobenzene (CB) and pure EA. With optimized proportion of EA and PE, the supersaturation degree is controlled via reducing the solvent evaporation rate and the nucleation rate, and it is good for crystal growth. Moreover, the grain growth rate and grain size are easily regulated, which contribute to the uniform, large grain and non-pinhole perovskite film. Correspondingly, the intrinsic perovskite solar cells based on CH3NH3PbI3 achieve a power conversion efficiency of 17.19% and an average efficiency of 16.25% (std 0.43).

Green Anti-solvent Processed Efficient Flexible Perovskite Solar Cells

Flexible perovskite solar cells (PSCs) possess compatible features with low-cost, high throughput production approaches, showing great potentials in wearable, portable, flyable, and deployable applications. However, flexible PSCs with superior efficiency are commonly fabricated with an anti-solvent assisted crystallization (ASAC) method, which uses highly toxic solvents as the processed solvents. In this work, we use environmentally benign anti-solvents for the fabrication of flexible PSCs. Benefiting from the low-temperature solution processability of a high quality SnO2 electron transport layer (ETL) with superior electron extraction and transfer features, flexible PSCs show an impressive PCE over 17% under reverse scan. This, to the best of our knowledge, is among the highest performances for flexible PSCs and is the first report for flexible PSCs fabricated by green anti-solvent processed techniques. These results provide new opportunities for environmental-friendly manufacturing of high performance f...

Improving the Performance and Reproducibility of Inverted Planar Perovskite Solar Cells Using Tetraethyl Orthosilicate as the Antisolvent.

Antisolvent-assisted crystallization has been extensively used for perovskite solar cells (PSCs), although this approach has a fatal drawback, low reproducibility, originating from the extremely harsh operating conditions of the current antisolvents. As a result, only skilled technicians are qualified to be scheduled to prepare perovskite thin films to fabricate high-efficiency devices, which lowers the pace of progress of PSCs. Besides, the most popular antisolvents toluene (TL) and chlorobenzene (CB) are highly toxic and carcinogenic. On account of these, we tried to develop a low hazardous antisolvent that enabled us to achieve highly efficient and highly reproducible PSCs. Herein, tetraethyl orthosilicate (TEOS) was employed in the inverted NiO X-based planar PSC for engineering an efficient perovskite layer, achieving a power conversion efficiency of 17.02% on glass substrates and 14.49% on flexible polymer substrates with negligible hysteresis, which even outperformed TL and CB. More importantly, TEOS PSCs exhibited much higher reproducibility than that of their counterparts. These desirable features should be ascribed to the higher-quality perovskite films with larger grain size, reduced density of defects, and thus smoother carrier transportation and slower carrier recombination. This work drives another step toward industrial-scale commercialization of PSCs and also paves the way for environmentally friendly photovoltaic applications.

High performance perovskite light-emitting diodes realized by isopropyl alcohol as green anti-solvent

Organic-inorganic hybrid perovskites (OIHPs) have been emerged as promising emitting materials for light-emitting diodes due to their miraculous optoelectronic properties. In pursuit of high perovskite quality, anti-solvent assisted crystallization (ASAC) is currently one of the most widely used low-energy consumption methods. However, traditional large-volume use of ASAC anti-solvent, such as chlorobenzene (CB), chloroform (CF), are hazardous to both the environment and human beings. Therefore, the development of green solvent for the ASAC will be of great important for the fabrication of perovskite light emitting diodes (PeLEDs) in more sustainable and environmental friendly ways. Herein, we employ a green solvent, isopropyl alcohol (IPA), as anti-solvent in ASAC for the first time, resulting in a high efficient PeLEDs with a maximum luminance of 7960 cd m−2, a current efficiency of 2.2 cd A−1, and a low turn-on voltage of 2 V. Compared to traditional toxicity solvents, IPA based ASAC leads to smoother surfaces and smaller grains of perovskites, while keeping the same crystallization features. Our results demonstrate that IPA is an excellent green ASAC anti-solvent alternative for high-quality perovskite film, and thus providing a novel opportunity for the low-cost and eco-friendly fabrication of PeLEDs.

Green Anti‐Solvent Processed Planar Perovskite Solar Cells with Efficiency Beyond 19%

Anti‐solvent assisted crystallization (ASAC) is currently one of the most widely used methods to obtain perovskite films with great quality due to its advantage of low cost and easy operation. The commonly used anti‐solvents, toluene, and chlorobenzene (CB), are well recognized to be contaminants in drinking water and exhibit high toxicity levels. It is desirable to develop environmentally benign solvents for the fabrication of perovskite solar cells by ASAC method. As a green solvent, methoxybenzene (PhOMe) has the advantages of low toxicity, moderate saturated vapor pressure, and similar solvent features with toluene and CB. Here, we report highly efficient planar perovskite solar cells (PSCs) prepared by ASAC method using PhOMe green anti‐solvent, achieving a power conversion efficiency (PCE) of 19.42%, which is better than CB processed PSCs (19.09%). Compared to CB processed perovskite films, perovskites produced by PhOMe exhibit smoother surfaces, larger grains, and lower carrier recombination rates, while the crystallization and absorption features remain basically unchanged. These results demonstrate that PhOMe is an excellent anti‐solvent alternative for high‐quality perovskites and thus provide new opportunities for environmental‐friendly manufacturing of PSCs and other optoelectronic devices.

Anti‐Solvent Assisted Crystallization Processed Methylammonium Bismuth Iodide Cuboids towards Highly Stable Lead‐Free Perovskite Solar Cells

AbstractIn the present investigation, lead–free methylammonium bismuth iodide ((CH3NH3)3Bi2I9) (MAIB) perovskite cuboids has been synthesized by antisolvent assisted crystallization solution process (ASACP). The optical measurements showed a strong absorption band around 550 nm with 2.1 eV band gap. The fabricated mesoporous type device showed good performance with current density (JSC) over 1.10 mAcm−2, open circuit voltage (VOC) 0.653 V, fill factor (FF) 0.496 with 0.356 % power conversion efficiency (PCE) which is much higher than convetional processed (CP) i. e. 0.069 %. Further these devices were studied for their air and moisture stability and our device shows excellent high stability more than 60 days.

Room temperature fabrication of CH3NH3PbBr3 by anti-solvent assisted crystallization approach for perovskite solar cells with fast response and small J–V hysteresis

Anti-solvent assisted crystallization (ASAC) approach was used to synthesize crystalline CH3NH3PbBr3 thin films with uniform microstructures through accelerated crystallization process at room temperature. The influence of different solvents and various interval dropping time on the final morphology was investigated. Photovoltaic devices with TiO2/CH3NH3PbBr3/spiro-MeOTAD structure were fabricated using ASAC approach without any post-annealing process. The devices were found to exhibit fast photocurrent response and small J–V hysteresis due to the room temperature processing that minimizes the formation of surface electron traps and corresponding slow transient current. The ASAC-CH3NH3PbBr3 solar cells exhibited open circuit voltage of 1.42V with champion power conversion efficiency (PCE) of 8.29%, much higher than the devices fabricated without using anti-solvent approach having a Voc of 1.01V and PCE of 3.15%. Our results demonstrate that ASAC approach can provide high performance room temperature fabrication method for low-cost perovskite solar cells.