Wide Process Window Research Articles

Low-pressure accessible gas-quenching for absolute methylammonium-free perovskite solar cells

Gas-quenching with tetramethylene sulfoxide (TMSO) enables a wide gas pressure processing window and superior accessibility to low-pressure processing for high-efficiency absolute MA-free perovskite solar cells.

Oxidation induced ductility enhancement of Zr based metallic glass ribbons in vicinity of glass transition temperature

Zr-based metallic glasses (MGs) possess a wide supercooled liquid region, which gives a wide processing window for superplastic forming to make microdevices with demanding size accuracy and surface finishing. The existence of oxygen may have an influence on the thermoplastic deformation process. Therefore, the effect of oxidation on the mechanical behavior of the MGs in the vicinity of glass transition temperature is of great significance for practical forming of MG components. In the present study, the effect of oxidation on tensile properties of Zr50Cu40Al10 metallic glass was investigated. The tested samples were characterized by XRD and SEM analysis. For the samples tested in air, the strength decreases 187 MPa, 61 MPa and 59 MPa and the ductility increases 0.31, 0.36, and 0.77 at 420 °C, 430 °C, and 440 °C, respectively, compared with those tested in flowing argon. ZrO2 preferentially formed during the tensile testing at 420 °C, and both ZrO2 and Al2O3 oxides formed at 430 °C. The dilution of Zr elements in the remaining amorphous matrix caused by preferential oxidation on the surface layer attributes to the decrease in strength and enhancement in ductility of the Zr50Cu40Al10 metallic glasses.

Large‐Area Organic Solar Modules with Efficiency Over 14%

AbstractIt is still challenging to fabricate efficient large‐area organic solar modules by solution processing. Processing window is important to obtain optimal aggregation of an active layer in large area for high efficiency. The star active layer of PM6:Y6 is processed from chloroform (for high efficiency) that has a narrow processing window due to the low boiling point of the solvent. In this work, the correlation between chemical structure (side chains) and processing solvents is investigated to obtain high efficiency and long processing windows. It is found that large side chains on the pyrrole ring are the key factor influencing the aggregation of active layer films. Short side chain (in Y6 and Y6‐1O) will cause excess aggregation when processed from high‐boiling‐point solvent (chlorobenzene, CB), while long side‐chain (in BTP‐BO‐4F, BTP‐BO‐4Cl, and BTP‐eC9) can inhibit such aggregation and maintain high photovoltaic performance when processed from CB with wide processing window. In the end, over 25 cm2 organic solar module via doctor blading based on PM6:BTP‐eC9 active layer has been fabricated with a PCE of 14.07%.

An easy-to-process poly(silylene-acetylene) terminated by reactive ethynylphenyl: Synthesis, properties and composites

A series of telechelic silicon-containing hybrid polymers with reactive ethynylphenyl terminals were synthesized using the Grignard reagent method. The structure, processability, curing behavior, thermal stability and dielectric properties of the polymers, as well as the mechanical properties of carbon fiber reinforced composites at room temperature and high temperature, were well characterized. The results indicate that the ethynylphenyl-terminated poly(silylene acetylene)s (EPTSAs) have wide processing window and stable viscosity for 6 h at 70 °C. The cured EPTSAs exhibit excellent thermooxidative stabilities with temperatures of 5% weight loss (Td5) and the residues at 800 °C (Yr800). The thermal stability of the cured EPTSAs can increase markedly with incorporation of Si-H groups. The Td5 and Yr800 of the cured EPTSAs could reach to 601 °C and 52% in air, respectively. The pyrolysis behavior of cured EPTSAs elucidates the cure reactions and cross-linked networks. The cured resins show excellent dielectric properties in the frequency range of 10–106 Hz. Furthermore, the glass transition temperature of the cured EPTSAs do not arise before 500 °C. The flexural strength and modulus of the carbon fiber cloth (T300CF) reinforced EPTSAs composites could reach 252 MPa, and 42 GPa. The retention of mechanical properties of the composite at 300 °C can reach to 89%.

Deep-Red Perovskite Light-Emitting Diodes Based on One-Step-Formed γ-CsPbI3 Cuboid Crystallites.

Inorganic CsPbI3 perovskite with high chemical stability is attractive for efficient deep-red perovskite light-emitting diodes (PeLEDs) with high color purity. Compared to PeLEDs based on ex-situ-synthesized CsPbI3 nanocrystals/quantum dots suffering from low conductivity and efficiency droop under high current densities, in situ deposited 3D CsPbI3 films from precursor solutions can maintain high conductivity but show high trap density. Here, it is demonstrated that introducing diammonium iodide can increase the size of colloids in the precursor solution, retard the phase-transition rate, and passivate trap states of the in-situ-formed cuboid crystallites. The PeLED based on the one-step-formed 3D CsPbI3 cuboid crystallite films shows a peak external quantum efficiency (EQE) value up to 15.03% because of the high conductivity and reduced trap states. Furthermore, this one-step method also has a wide processing window, which is attractive for flow-line production of large-area PeLED modules. The fabrication of a 9 cm2 PeLED that exhibits a peak EQE of 10.30% is successfully demonstrated.

Segregation engineering of grain boundaries of a metastable Fe-Mn-Co-Cr-Si high entropy alloy with laser-powder bed fusion additive manufacturing

Laser-powder bed fusion (L-PBF) additive manufacturing offers unprecedented microstructural fine-tuning capabilities. Naturally, benefitting from such capability requires alloys that are amenable to microstructural heterogeneity and hierarchy (MHH) and that exhibit a low hot-cracking susceptibility (HCS). However, columnar growth, which is characterized by capillary effects and poor strain accommodation capabilities, is prevalent in L-PBF and increases the HCS of the processed alloys. Further, while solute segregation is prominent in cellular and dendritic growth modes during L-PBF, the effects of solute segregation on the alloy HCS and L-PBF processing window remain widely unexplored. Here, we demonstrate that solute segregation affects columnar growth, grain coalescence behavior during solidification, MHH and mechanical properties of a metastable Fe40Mn20Co20Cr15Si5 (at.%) high entropy alloy (CS-HEA) doped with 0.5 wt.% B4C (termed CS-BC). A theoretical framework is proposed, which reveals that a boundary-strengthening segregant may reduce the alloy HCS during L-PBF. In as-built CS-BC, boron, a boundary strengthener, segregated to the solidification cell boundaries, whereas carbon remained in the solid solution. The as-built CS-BC exhibited suppressed columnar growth, more random texture, smaller cell size and higher strength as compared to the as-built CS-HEA. Further, a wide crack-free L-PBF processing window of CS-BC allowed fine-tuning of its MHH and thus the mechanical properties. Upon annealing, as carbon-containing precipitates formed, CS-BC exhibited a metastable microstructure and transformation induced plasticity effect, which led to high synergistic strength-ductility. These findings will foster design of alloys that facilitate application-specific manufacture with L-PBF and thus, an extended outreach of L-PBF for structural applications.

In Situ Compatibilization of Isotactic Polypropylene and High-Density Polyethylene by a Melt Cobranching Reaction

Incompatible polypropylene (PP) and polyethylene (PE) are difficult to separate in mixed recycling streams such as waste plastic packaging, which makes polyolefin mixtures unsuitable for high-quality products. In this work, based on the free radical branching reaction, a co-branching reaction of isotactic polypropylene (iPP) and high-density polyethylene (HDPE) blends was carried out in the presence of the peroxide, free radical regulator and multifunctional acrylate monomer, and a star-like long-chain branching (LCB) copolymer was obtained. The effect of in situ compatibilization on the structures and mechanical properties of iPP/HDPE was investigated, and the compatibilization mechanism was discussed. Results showed that the mechanical properties of the modified blends were largely improved, and efficient in-situ compatibilization of iPP and HDPE could be taken place in a wide process window. Moreover, the sizes of the dispersed phase in the modified blends were clearly decreased, and the interfacial thickness increased. Compared with the pure iPP/HDPE blend, the initial crystallization temperature of iPP in the modified iPP/HDPE blend was increased, and long branched chains of the LCB copolymers were physically entangled with the chemical identical homopolymers or even participated in the crystallization of iPP and HDPE. Thanks to the in situ compatibilization strategy, the compatibility of iPP/HDPE was significantly improved.

Self-Aligned Assembly of a Poly(2-vinylpyridine)-b-Polystyrene-b-Poly(2-vinylpyridine) Triblock Copolymer on Graphene Nanoribbons.

Directed self-assembly (DSA) of block copolymers is one of the most promising patterning techniques for patterning sub-10 nm features. However, at such small feature sizes, it is becoming increasingly difficult to fabricate the guiding pattern for the DSA process, and it is necessary to explore alternative guiding methods for DSA to achieve long-range ordered alignment. Here, we report the self-aligned assembly of a triblock copolymer, poly(2-vinylpyridine)-b-polystyrene-b-poly(2-vinylpyridine) (P2VP-b-PS-b-P2VP) on neutral graphene nanoribbons with the gap consisting of a P2VP-preferential silicon oxide (SiO2) substrate via solvent vapor annealing. The assembled P2VP-b-PS-b-P2VP demonstrated long-range, one-dimensional alignment on the graphene substrate in a direction perpendicular to the boundary of the graphene and substrate with a half-pitch size of 8 nm, which greatly alleviates the lithography resolution required for traditional chemoepitaxy DSA. A wide processing window is demonstrated with the gap between graphene stripes varying from 10 to 100 nm, overcoming the restriction on widths of guiding patterns to have commensurate domain spacing. When the gap was reduced to 10 nm, P2VP-b-PS-b-P2VP formed a straight-line pattern on both the graphene and the substrate. Monte Carlo simulations showed that the self-aligned assembly of the triblock copolymer on the graphene nanoribbons is guided at the boundary of parallel and perpendicular lamellae on graphene and SiO2, respectively. Simulations also indicate that the swelling of a system allows for rapid rearrangement of chains and quickly anneal any misaligned grains and defects. The effect of the interaction strength between SiO2 and P2VP on the self-assembly is systematically investigated in simulations.

A high-performance silicon-containing arylacetylene resin with conjugated naphthalene rings

2,7-Diphenyloxynaphthalene with large conjugated structure has been introduced into the main chain of silicon-containing arylacetylene resin and then poly(dimethylsilylene-ethynylenephenoxynaphthyloxyphenylene-ethynylene) ( m-PPNSA-MM) was synthesized. The m-PPNSA-MM resin shows good solubility and a wide processing window. A stable three-dimensional cross-linking network formed due to thermal crosslinking reactions of acetylene groups and intermolecular π–π stacking interactions after m-PPNSA-MM was cured through the process of 180°C/2 h + 220°C/2 h + 260°C/4 h. The flexural strength and modulus of the cured m-PPNSA-MM resin at room temperature are 49.2 MPa and 2.75 GPa, respectively. The cured m-PPNSA-MM resin show high thermal stabilities, the 5% temperature of weight loss ( Td5) reaches 560°C in nitrogen.

Synthesis and unique characteristics of biobased high Tg copolyesters with improved performance properties for flexible electronics and packaging applications

The synthesis and characterization of two series of biobased novel poly(1,4-cyclohexylenedimethylene terephthalate-co-1,4-cyclohexylene dimethylene 2,6-naphthalenedicarboxylate) copolyesters containing isosorbide (ISB) content (PCITN) ranging from 0 to 11 mol% relative to the total diol amount was carried out in this study. The Novel PCITN was containing 2,6-naphthalenedicarboxylic acid (NDA) content ranging from 0 to 100 mol% relative to the total diacid amount. The synthesized PCITN were thoroughly characterized for their actual chemical composition, molecular weight, thermal properties, thermal stability, dimensional stability, transmittance (%), and birefringence. All the copolyesters showed the characteristics of random copolyesters and their composition and thermal properties could be controlled by the molar feed ratio of diol and diacid moieties. Results indicate that ISB significantly improves the glass transition temperature (Tg) of resultant copolyesters. It was also found that synthesized copolyesters have a high Tg and wide processing window compared to conventional homopolyesters. Exceptional performance properties: such as high Tg, Tm, high thermal stability, dimensional stability, good moisture barrier, good transmittance, and low birefringence of fabricated PCI6TN70 film, make it suitable for versatile industrial applications especially for biomedical, packaging, and optical applications.

Mechanical Properties and Interface Microstructure of SAC305 Solder Joints Made to a Ag-Pd-Pt Thick Film Metallization: Part 2—Isothermal Aging Effects

Abstract The performance and reliability were documented for solder joints made between the 96.5Sn-3.0Ag-0.5Cu (wt.%, abbreviated SAC305) Pb-free solder and a Ag-Pd-Pt thick film conductor on an alumina substrate. The Sheppard’s hook pull test was used to assess the solder joint strength. The Part 1 study confirmed that the solder joint fabrication process had a wide process window. The current study determined that the SAC305 solder joints maintained that robustness after accelerated aging at temperatures of 70–205°C and time durations of 5–200 d. Short-term aging of 5–10 d caused a peak in the pull strength peak that resulted from precipitation hardening by Ag-Pd and (Pd, Pt)xSny intermetallic compound (IMC) particles. The pull strengths did not decrease significantly after longer aging times at 70°C and 100°C; those conditions were accelerations of typical service lifetimes. Longer aging times at temperatures of 135–205°C resulted in a gradual, albeit not catastrophic, strength decrease when the precipitation hardening mechanism was lost to dissolution of the particle phases and their reprecipitation at the solder/alumina interface. The failure modes were ductile fracture in the solder except for the most severe aging conditions. These findings confirmed that the SAC305 solder/Ag-Pd-Pt thick film interconnections have excellent long-term reliability for hybrid microcircuit and high-temperature electronics applications.

Fabrication and characterization of high-performance Mo-doped TiN coatings

To realize the fabrication of Ti–Mo–N coatings with novel properties predicted towards industrial applications, Mo-doped TiN coatings have been fabricated by multi-arc ion plating with varied substrate bias, and systematically characterized. The as-deposited coatings show a 1.5 at% Mo content deficit due to melting point difference between Mo and Ti elements. X-ray diffraction (XRD) and X-ray photoelectron spectrum (XPS) results show the as-deposited coatings demonstrate a fcc-TiN + bct-Ti2N dual phase structure, with Mo solution into TiN lattice. The hardness of TiMo0.08N coatings is above 31.97 GPa, which first increases then decreases slightly, peaking at 34.26 GPa. The phenomenon is correlated to the decreased (111) while enhanced (220) preferred orientation. All coatings show adhesion properties above 65 N (>100 N when bias voltage is above −50 V) and friction coefficients (COFs) below 0.24, which is attributed to the formation of lubricant MoO3 phase in a surface tribochemical process, as confirmed by XPS and Raman spectra evidences. Electrochemical polarization curves reveal that all samples have higher corrosion potential and corrosion currents two order of magnitudes lower than the WC-Co substrates. Additionally, substrate bias voltage has little impacts on structures and properties of the coatings, which means a wide process window.

Natural magnolol derivatives as platform chemicals for bio-based phthalonitrile thermoset: Achieving high performances without an external curing agent

Bio-based polymers with better comprehensive properties, showing more competitiveness than their petroleum-based counterparts in high-tech fields is an increasingly trend but also a formidable challenge. In the study, bio-based phthalonitrile precursors were synthesized from natural occurring magnolol derivatives through a highly efficient one step process. Self-curing reactions can be proceeded with allyl groups in the resultant precursors without sacrificing the thermal stabilities of the thermoset resins. The curing behavior, mechanism and processability of the phthalonitrile precursors were studied, and the thermal stabilities of cured polymers were evaluated. Of the two bio-based precursors, the honokiol derivate exhibited a wide processing window of 163 °C with a melting point lower than 70 °C. After curing, both the magnolol- and honokiol-based resins showed glass transition temperature higher than 500 °C and 5% weight loss temperature as high as 527 °C. These properties were superior to those of the petroleum-based reference without allyl group. A model reaction, showed that the curing mechanism of allyl/phthalonitrile system here was considered to be free radical polymerization. The results demonstrate that sustainable magnolol derivatives can be employed as platform chemicals to impart excellent performances to the bio-based polymers for great promise in cutting-edge applications.

Design of heterogeneous structured Al alloys with wide processing window for laser-powder bed fusion additive manufacturing

Required microstructural attributes of an alloy vary with structural applications. The microstructural fine-tuning capability of laser-powder bed fusion (L-PBF) additive manufacturing (AM) enables application specific manufacture of the components. Such manufacture with L-PBF AM requires alloys that exhibit wide processing window and are amenable to multiple deformation mechanisms. However, high hot cracking susceptibility of Al alloys poses a barrier to such printability-performance synergy. In this work we show that an integration of, a) grain refinement through heterogeneous nucleation, and b) eutectic solidification, leads to crack-free parts at wide range of process parameters, microstructural heterogeneity, and hierarchy in the Al-Ni-Ti-Zr alloy. Such an integration targets hot cracking at multiple stages of solidification in L-PBF as opposed to the contemporary alloy design strategies that target hot-cracking at only specific stages of solidification. The Al-Ni-Ti-Zr alloy exhibits excellent printability and a high as-built tensile performance. Due to the wide processing window and amenability to multiple deformation mechanisms, the alloy microstructure and subsequently the performance, can be fine-tuned. Such strategy opens the gateway for application-specific manufacture of Al alloys with L-PBF AM and establishes a fundamental shift in current methodologies for design of these alloys for L-PBF AM.

High-performance polymers adapted to facile melt processing through structure design of benzocyclobutene-containing precursors

High-performance polymeric materials with good processability and enhanced performance (higher thermal stability and mechanical strength, higher glass transition temperature (Tg) and lowered thermal expansion) have long been explored by scientists and engineers. The present study demonstrated a new way to fabricate high-performance polymers, such as polyarylamide (traditional polyarylamides can’t be processed by melt processing due to the lack of viscous flow temperature before thermal decomposition), with excellent processability via a facile two-step process, i.e. low-temperature melt processing and a subsequent in-situ thermal curing. Through designing the structure of the BCB-containing precursors, we can well control the melting point and curing temperature, thus adjust the melt processing temperature and curing temperature of the polymers. In our experiments, the temperature difference between precursor melting point and polymerization temperature can be over 200 °C, providing wide processing window and long storage lifetime. Besides, these precursors also possess excellent solubility in organic solvents, which endow them with the possibility of solution or melt processing, as illustrated by the representative precursor, DODA-BCB. The obtained polymer resin films show good thermal stability (Td,5% > 410 °C), high glass transition temperatures (Tg > 240 °C) and good mechanical strength (storage modulus > 1.8 GPa). Further studies on the thermal expansion behavior of the films reveal the thermal contracting feature of p-3,4′-ODA-BCB, the mechanism has been discussed in detail using DFT calculations, VT-FTIR and TMA.

A simple one-step method with wide processing window for high-quality perovskite mini-module fabrication

<h2>Summary</h2> The one-step antisolvent approach is a widely employed method for fabricating perovskite devices at a low cost. However, the current antisolvent approach requires a strict set of processing conditions to obtain high-quality perovskite layers. Here, we introduce sulfolane as an additive in the perovskite precursor to convert the perovskite phase via a new reaction route, providing a large degree of flexibility to process crystalline perovskite layers with high uniformity on a large scale. As it is revealed by X-ray diffraction and Fourier-transform infrared spectroscopy findings, we find that the key concept lies in intermolecular hydrogen-bonding forces' interaction between sulfolane and methylammonium iodide, which slows down the nucleation and subsequently the crystallization process. As a result, we demonstrate a mini module, 36.6 cm² active area, and achieve a record PCE of 16.06%. More importantly, the encapsulated mini module retained about 90% of the initial performance after operating at the maximum power point under simulated AM1.5G irradiation for 250 h at 50°C.

Efficient p-n Heterojunction Perovskite Solar Cell without a Redundant Electron Transport Layer and Interface Engineering.

We report an electron transport layer-free perovskite solar cell (PSC) without interface engineering, whose key is a p-n heterojunction consisting of ITO/n-type FA0.9Cs0.1PbI3-xClx/p-type spiro-MeOTAD/Ag. The naturally matched energy levels between FA0.9Cs0.1PbI3-xClx and ITO make interface engineering unnecessary. The FA0.9Cs0.1PbI3-xClx film has a wide antisolvent processing window, favoring large-area production. The self-seeding growth method regulates the energy levels and work function of the FA0.9Cs0.1PbI3-xClx film via modulating the shape and distribution of residual PbI2. Interface band bending is confirmed by double-side photoluminescence (PL) measurement. Reduced PL is introduced for unambiguous charge transfer analysis without interference caused by different absorbance. Accordingly, enhanced ITO/perovskite interface energy level alignment and device performance (efficiency of 17.48% and Voc of 1.02 V) are demonstrated. Such simplified but efficient PSCs featuring a wide antisolvent processing window have great potential in practical applications.

Effects of Wire Diameter and Filament Size on the Processing Window of Bi-2212 Round Wire

High engineering critical current density (JE of 1300 A/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 4.2 K and 15 T) in Bi-2212 round wire has been achieved through a partial melt, overpressure heat treatment process. JE varies strongly with processing conditions, particularly the maximum heat treatment temperature (Tmax). Increasing Tmax results in longer time in the melt (defined as the time between when Bi-2212 melts on heating and when Bi-2212 begins to form on cooling), more bridging between the filaments, lower JE, and higher ac losses. A wide processing window with a large range of Tmax that has a nearly constant JE is desired for processing large coils with large thermal mass and significant thermal time constants that may make precise control over the desired temperature - time profiles uncertain. Accordingly, we wanted to explore broadening the Tmax window by controlling the Bi-2212 powder melting or wire architecture design. Here we report on studies of the performance variation with Tmax for two production wires with a filling factor of about 20% and 85 × 18 filaments where filament size was varied by changing the wire diameter, a process which also shortens the distance between filaments. We found that wires with smaller filament diameter (9 to 11 μm) showed a peak JE at the low end of Tmax and also a JE that was more sensitive to Tmax. A JE - Tmax plot showed a plateau JE(4.2 K, 5 T) of ~1100 A/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> between Tmax of 886 and 894 °C for 1.0 and 1.2 mm wires, where JE is less sensitive to the wire diameter and Tmax. This JE plateau range is a preferred processing window for achieving high JE in coils.

SMART Perovskite Growth: Enabling a Larger Range of Process Conditions

Cost-effective, high-throughput industrial applications of metal-halide perovskites require a highly tolerant method (i.e., wide process window) that produces high-quality materials with a short an...

Three-state lithography model: an enhanced mathematical approach to predict resist characteristics in grayscale lithography processes

Background: Physical modeling of grayscale lithography processes for the prediction of photoresist heights leads to complex mathematical algorithms. A promiment example is the numerical simulation of the photoresist shape after development through Dill’s equations. These grayscale lithography models exhibit accurate prediction quality but can not directly implemented into mask layout tools to simplify the layout procedure. Limited process windows, changes in the mask design, variations of the used materials or manufacturing tools lead to time-consuming and cost-intensive test procedures to adjust the photoresist model for sufficient results. Aim: The focus of this work is to enhance current grayscale lithography models for a straightforward method with the same precise prediction of remaining photoresist heights to simplify the mask layout process. Moreover, we aim for an uncomplicated optimization of the model to minimize the empirical analysis necessary for its use. Approach: Based on experimental results, we deploy a sectionally defined mathematical expression that includes the theory of Fraunhofer diffraction and illumination-dependent activation of the photo-sensitive component and its solubility in developer. Results: We produced pyramidal, spherical and chess field structures with exposure doses of 3000 and 15 , 000 J / m2 on bare silicon substrates with 100-nm resolution and on silicon substrates with anti-reflective coatings, with accuracy as fine as 20 nm. Conclusion: The proposed three-state lithography model has been verified by experimental evaluation. It is able to operate in a wide process window and can be directly implemented in existing mask layout software. This model ensures a cost-efficient and precisely controlled production of three-dimensional topographies using grayscale lithography processes.