Toluene Processed All-Polymer Solar Cells with 18%Efficiency and Enhanced Stability Enabled by Solid Additive:Comparison Between Sequential-Processing and Blend-Casting

The emergence of polymerized small molecule acceptors(PSMAs)has significantly improved the performance of all-polymer solar cells(all-PSCs).However,the pace of device engineering lacks behind that of materials development,so that a majority of the PSMAs have not fulfilled their potentials.Furthermore,most high-performance all-PSCs rely on the use of chloroform as the processing solvent.For instance,the recent highperformance PSMA,named PJ1-γ,with high LUMO,and HOMO levels,could only achieve a PCE of 16.1%with a high-energy-level donor(JD40)using chloroform.Herein,we present a methodology combining sequential processing(SqP)with the addition of 0.5%wt PC_(71)BM as a solid additive(SA)to achieve an impressive efficiency of 18.0%for all-PSCs processed from toluene,an aromatic hydrocarbon solvent.Compared to the conventional blend-casting(BC)method whose best efficiency(16.7%)could only be achieved using chloroform,the SqP method significantly boosted the device efficiency using toluene as the processing solvent.In addition,the donor we employ is the classic PM6 that has deeper energy levels than JD40,which provides low energy loss for the device.We compare the results with another PSMA(PYF-T-o)with the same method.Finally,an improved photostability of the SqP devices with the incorporation of SA is demonstrated.

Solid Additive-Assisted Layer-by-Layer Processing for 19%Efficiency Binary Organic Solar Cells

Morphology is of great significance to the performance of organic solar cells(OSCs),since appropriate morphology could not only promote the exciton dissociation,but also reduce the charge recombination.In this work,we have developed a solid additive-assisted layer-by-layer(SAA-LBL)processing to fabricate high-efficiency OSCs.By adding the solid additive of fatty acid(FA)into polymer donor PM6 solution,controllable pre-phase separation forms between PM6 and FA.This intermixed morphology facilitates the diffusion of acceptor Y6 into the donor PM6 during the LBL processing,due to the good miscibility and fast-solvation of the FA with chloroform solution dripping.Interestingly,this results in the desired morphology with refined phase-separated domain and vertical phase-separation structure to better balance the charge transport/collection and exciton dissociation.Consequently,the binary single junction OSCs based on PM6:Y6 blend reach champion power conversion efficiency(PCE)of 18.16%with SAA-LBL processing,which can be generally applicable to diverse systems,e.g.,the PM6:L8-BO-based devices and thick-film devices.The efficacy of SAA-LBL is confirmed in binary OSCs based on PM6:L8-BO,where record PCEs of 19.02%and 16.44%are realized for devices with 100 and 250 nm active layers,respectively.The work provides a simple but effective way to control the morphology for high-efficiency OSCs and demonstrates the SAA-LBL processing a promising methodology for boosting the industrial manufacturing of OSCs.

High-efficiency organic solar cells enabled by an alcohol-washable solid additive

The solvent additive strategy has been widely utilized to boost the power conversion efficiency(PCE)of organic solar cells(OSCs).However,the residual solvent additive in the active layer tends to induce a gradual morphology degradation and further influences the long-term stability of OSCs.Here,a solid additive,1,4-diiodobenzene(DIB),was introduced to fabricate efficient OSCs.We found that the treatment of DIB can lead to optimized morphology to form a bicontinuous network with intensified intermolecular packing in the donor and acceptor phases.Notably,DIB can be easily removed from the active layer via a simple alcohol washing process and no further post-thermal annealing is needed,which is desirable for large-scale manufacturing of OSCs.As a result,high efficiencies of 17.47%for PM6:Y6 and 18.13%(certified as 17.7%)for PM6:BTP-eC9 binary OSCs are achieved,which are among the highest efficiencies reported for binary OSCs thus far.Moreover,OSCs fabricated with DIB also exhibit superior stability compared with the as-cast and traditional solvent additive processed devices.Additionally,DIB was successfully applied in different active layers,manifesting its general applicability.This work provides a feasible approach to enhance both the efficiency and stability of OSCs.

Synergistic effect of solvent and solid additives on morphology optimization for high-performance organic solar cells

Controlling the photoactive layer morphology towards nanoscale bi-continuous donor/acceptor interpenetrating networks is a key issue to build high-performance organic solar cells(OSCs).Due to the distinct properties between donor and acceptor materials,casting an active layer from a single solvent solution usually results in either insufficient or excessive phase separation that reduces the device performance.In comparison to the fullerene acceptors with closed-cage structures,the currently dominant non-fullerene acceptors possess the similar anisotropicπ-πinteractions with p-type organic semiconductor donors,giving rise to the complexity of the morphology regulation.Herein,we employ 4,4′-dimethoxyoctafluorobiphenyl(OFP)with strong crystallinity as a volatile solid additive to optimize the active layer morphology of OSCs.The synergistic effect of 1-chloronaphthalene(CN)and OFP as dual additives shows supreme capability on optimizing the morphology over the conventional additive of CN,which is in favor of improving charge transport and suppressing charge recombination for higher fill factors in various systems.In particular,the PTQ10:m-BTP-C6 Ph-based device processed by the additive showed a remarkable powerconversion efficiency(PCE)of 17.74%,whereas the control device processed by CN additive yielded a relatively lower PCE of16.45%.

An Organic Small Molecule as a Solid Additive in Non-Fullerene Organic Solar Cells with Improved Efficiency and Operational Stability

The use of additive is an effective approach to optimize the active layer morphology and improve the power conversion efficiency(PCE)of organic solar cells(OSCs).However,residual solvent additives always lead to undesirably compromise the stability of OSCs.In this work,an organic small molecule BBT-Cl was designed and used as a novel solid additive to partly replace solvent additive to fabricate highperformance OSCs.The synergistic effect of the dual additives on the optical property,morphology and photovoltaic characteristics of the PM6:Y6 based non-fullerene OSCs have been systematically characterized.The introduction of BBT-Cl could effectively enhance the crystallinity of the blend and promote charge extraction and transport.Consequently,the OSCs processed by the dual additives exhibit a high PCE of 17.73%,which is obviously higher than OSCs with CN additive(16.48%).Meanwhile,BBT-Cl based dual additives treatment has also been successfully introduced into another two non-fullerene OSCs to verify its general applicability.Furthermore,20%PCE aging is significantly prolonged from 720 min to 2880 min for the devices proceeded with the dual additives.This work highlights the great potential of solid additive in the fabrication of efficient OSCs with excellent stability.

Additive friction stir deposition of AZ31B magnesium alloy

The current work explored additive friction stir deposition of AZ31B magnesium alloy with the aid of MELD?technology.AZ31B magnesium bar stock was fed through a hollow friction stir tool rotating at constant velocity of 400 rpm and translating at linear velocity varied from 4.2 to 6.3 mm/s.A single wall consisting of five layers with each layer of 140×40×1 mm^(3)dimensions was deposited under each processing condition.Microstructure,phase,and crystallographic texture evolutions as a function of additive friction stir deposition parameters were studied with the aid of scanning electron microscopy including electron back scatter diffraction and X-ray diffraction.Both feed material and additively produced samples consisted of theα-Mg phase.The additively produced samples exhibited a refined grain structure compared to the feed material.The feed material appeared to have a weak basal texture,while the additively produced samples experienced a strengthening of this basal texture.The additively produced samples showed a marginally higher hardness compared to the feed material.The current work provided a pathway for solid state additive manufacturing of Mg suitable for structural applications such as automotive components and consumable biomedical implants.

Pressure State in Deep Crust and Formation Depth of UHP Metamorphic Rocks

This paper presents some questions to the formula of pressure=depth×specific gravity from the viewpoint that the hydrostatic pressure is equal to the gravity of overlying rocks and the rocks in a static fluid state, which is drawn from the research and analysis of the research field and the corresponding problems of the pressure state in the deep crust and the formation depth of the UHP metamorphic rocks. In this research, the underground rocks are considered as the solid possessing some rheological behaviors to discuss the polysource stress state and to obtain a more reasonable method for the calculation of depths using the model of the unbalanced force solid. It is suggested from this paper that the P/SW method for the calculation of the ultrahigh pressure stemming only from the gravity has obviously overstated the formation depth of the UHP metamorphism. The formation model emphasizing the effect of the gravity, the tectonic force and the metamorphic force of the facies change concludes that such UHP minerals as coesite may have been produced in the inner crust.

3D printing of fine-grained aluminum alloys through extrusion-based additive manufacturing:Microstructure and property characterization

Additive manufacturing(AM)has the potential to transform manufacturing by enabling previously un-thinkable products,digital inventory and delivery,and distributed manufacturing.Here we presented an extrusion-based metal AM method(refer to“SoftTouch”depositionin thefiledpatent)thatis suitablefor making the metal feedstock flowable prior to the deposition through dynamic recrystallization induced grain refinement at elevated temperatures.The flowable metal was extruded out of the printer head like a paste for building dense metal parts with fine equiaxed grains and wrought mechanical properties.Off-the-shelf metal rods were used as feedstock and the printing process was completed in an open-air environment,avoiding pricy powders and costly inert or vacuum conditions.The resulting multi-layer de-posited 6061 aluminum alloys yield strength and ductility comparable to wrought 6061 aluminum alloys after the same T6 heat treatment.The extrusion-based metal AM method can also be advanced as green manufacturing technologies for fabricating novel alloys and composites,adding novel features to existing parts,repairing damaged metal parts,and welding advanced metals for supporting sustainable manufac-turing,in addition to being developed into a cost-effective manufacturing process for the fabrication of dense metal of complex structural forms.

Tribological Behavior of TiAl-Multilayer Graphene-Ag Composites at Different Temperatures and Sliding Speeds

Tribological behavior of TiAl-multilayer graphene-Ag composites （TMACs） prepared by spark plasma sin- tering against a Si3N4 ball was investigated on a ball-on-disk high-temperature tribometer at different test temperatures and sliding speeds in this study. The test results showed that TMACs had the lower friction coefficient and less wear rate at 450 ℃-0.25 m/s, which was attributed to the formation of the high-strength and intact tribofilms on worn surface. At 450 ℃-0.25 m/s, during the sliding process, multilayer graphene （MLG） was ground out to form the high-strength skeletons on the wom surface of TMACs. Ag was migrated from the worn surface and combined with the MLG skeleton to form the high-strength and intact tribofilms. The high-strength and intact tribofilms were beneficial to lowering the friction coefficient for the lubricating effect of Ag and decreasing wear rate for the enhancing effect of MLG skeleton.