The ancient wisdom found in iron gall ink guides this work to a simple but advanced solution to the molecular engineering of fluidic interfaces. The Fe(II)–tannin coordination complex, a precursor of ...the iron gall ink, transforms into interface‐active Fe(III)–tannin species, by oxygen molecules, which form a self‐assembled layer at the fluidic interface spontaneously but still controllably. Kinetic studies show that the oxidation rate is directed by the counteranion of Fe(II) precursor salts, and FeCl2 is found to be more effective than FeSO4—an ingredient of iron gall ink—in the interfacial‐film fabrication. The optimized protocol leads to the formation of micrometer‐thick, free‐standing films at the air–water interface by continuously generating Fe(III)–tannic acid complexes in situ. The durable films formed are transferable, self‐healable, pliable, and postfunctionalizable, and are hardened further by transfer to the basic buffer. This O2‐instructed film formation can be applied to other fluidic interfaces that have high O2 level, demonstrated by emulsion stabilization and concurrent capsule formation at the oil–water interface with no aid of surfactants. The system, inspired by the iron gall ink, provides new vistas on interface engineering and related materials science.
The in situ oxidation of Fe(II) to Fe(III) in the Fe(II)–tannin complex, inspired by iron gall ink, provides a simple but advanced solution to the molecular engineering of fluidic interfaces. The versatility of this O2‐instructed synthetic strategy is demonstrated by the formation of micrometer‐thick, free‐standing films at the air–water interface and hollow capsules at the oil–water interface.
High power conversion efficiency (PCE) and stretchability are the dual requirements for the wearable application of polymer solar cells (PSCs). However, most efficient photoactive films are ...mechanically brittle. In this work, highly efficient (PCE = 18%) and mechanically robust (crack‐onset strain (COS) = 18%) PSCs are acheived by designing block copolymer (BCP) donors, PM6‐b‐PDMSx (x = 5k, 12k, and 19k). In these BCP donors, stretchable poly(dimethylsiloxane) (PDMS) blocks are covalently linked with the PM6 blocks to effectively increase the stretchability. The stretchability of the BCP donors increases with a longer PDMS block, and PM6‐b‐PDMS19k:L8‐BO PSC exhibits a high PCE (18%) and 9‐times higher COS value (18%) compared to that (COS = 2%) of the PM6:L8‐BO‐based PSC. However, the PM6:L8‐BO:PDMS12k ternary blend shows inferior PCE (5%) and COS (1%) due to the macrophase separation between PDMS and active components. In the intrinsically stretchable PSC, the PM6‐b‐PDMS19k:L8‐BO blend exhibits significantly greater mechanical stability PCE80% ((80% of the initial PCE) at 36% strain) than those of the PM6:L8‐BO blend (PCE80% at 12% strain) and the PM6:L8‐BO:PDMS ternary blend (PCE80% at 4% strain). This study suggests an effective design strategy of BCP PD to achieve stretchable and efficient PSCs.
Polymer solar cells (PSCs) with high‐performance and ‐stretchability are developed by designing block copolymer donors comprising PM6 and elastomeric PDMS blocks (PM6‐b‐PDMS). High power conversion efficiency (PCE ≈ 18%) and stretchability (crack onset point > 18%) are demonstrated for the PM6‐b‐PDMS19k‐based PSC. The PM6‐b‐PDMS19k‐based intrinsically stretchable PSCs show superior mechanical stability (PCE retention > 80% at 32% strain) than the PM6‐based and PM6:PDMS‐blend‐based devices.
Direct measurement of the adhesion energy of monolayer graphene as-grown on metal substrates is important to better understand its bonding mechanism and control the mechanical release of the graphene ...from the substrates, but it has not been reported yet. We report the adhesion energy of large-area monolayer graphene synthesized on copper measured by double cantilever beam fracture mechanics testing. The adhesion energy of 0.72 ± 0.07 J m(-2) was found. Knowing the directly measured value, we further demonstrate the etching-free renewable transfer process of monolayer graphene that utilizes the repetition of the mechanical delamination followed by the regrowth of monolayer graphene on a copper substrate.
Graphene produced by chemical vapor deposition (CVD) has attracted great interest as a transparent conducting material, due to its extraordinary characteristics such as flexibility, optical ...transparency, and high conductivity, especially in next‐generation displays. Graphene‐based novel electrodes have the potential to satisfy the important factors for high‐performance flexible organic light‐emitting diodes (OLEDs) in terms of sheet resistance, transmittance, work function, and surface roughness. In this study, flexible and transparent graphene electrode architecture is proposed by adopting a selective defect healing technique for CVD‐grown graphene, which results in several benefits that produce high‐performance devices with excellent stabilities. The proposed architecture, which has a multi‐layer graphene structure treated by a layer‐by‐layer healing process, exhibits significant improvement in sheet resistance with high optical transparency. For improving the charge transport property and mechanical robustness, various defect sites of the CVD‐grown graphene are successfully decorated with gold nanoparticles through a simple electroplating (EP) method. Further, a graphene‐based OLED device that integrates the proposed electrode architecture on flexible substrates is demonstrated. Therefore, this architecture provides a new strategy to fabricate graphene electrode in OLEDs, extending graphene's immense potential as an advanced conductor toward high‐performance, flexible, and transparent displays.
Flexible and transparent graphene electrode architecture with layer‐by‐layer defect healing is proposed for the high‐performance graphene‐based flexible organic light‐emitting diodes. Improved performance including excellent charge transport and mechanical robustness of the proposed electrode architecture is systemically investigated, showing synergetic effects of selective defect healing and structural advantages. The new graphene electrode architecture demonstrates the great possibilities for flexible and transparent graphene‐based displays.
Intrinsically stretchable organic solar cells (IS‐OSCs), consisting of all stretchable layers, are attracting significant attention as a future power source for wearable electronics. However, most of ...the efficient active layers for OSCs are mechanically brittle due to their rigid molecular structures designed for high electrical and optical properties. Here, a series of new polymer donors (PDs, PhAmX) featuring phenyl amide (N1,N3‐bis((5‐bromothiophen‐2‐yl)methyl)isophthalamide, PhAm)‐based flexible spacer (FS) inducing hydrogen‐bonding (H‐bonding) interactions is developed. These PDs enable IS‐OSCs with a high power conversion efficiency (PCE) of 12.73% and excellent stretchability (PCE retention of >80% of the initial value at 32% strain), representing the best performances among the reported IS‐OSCs to date. The incorporation of PhAm‐based FS enhances the molecular ordering of PDs as well as their interactions with a Y7 acceptor, enhancing the mechanical stretchability and electrical properties simultaneously. It is also found that in rigid OSCs, the PhAm5:Y7 blend achieves a much higher PCE of 17.5% compared to that of the reference PM6:Y7 blend. The impact of the PhAm‐FS linker on the mechanical and photovoltaic properties of OSCs is thoroughly investigated.
Efficient, intrinsically stretchable organic solar cells (IS‐OSCs) are developed by designing a new series of polymer donors (PDs, PhAm) featuring hydrogen‐bonding‐capable flexible spacers. High power conversion efficiency (PCE = 12.7%) and stretchability (PCE retention of > 80% at 32% strain) are demonstrated, which represent the best performances in terms of both PCE and stretchability among the IS‐OSCs reported to date.
Stretchable organic light-emitting diodes are ubiquitous in the rapidly developing wearable display technology. However, low efficiency and poor mechanical stability inhibit their commercial ...applications owing to the restrictions generated by strain. Here, we demonstrate the exceptional performance of a transparent (molybdenum-trioxide/gold/molybdenum-trioxide) electrode for buckled, twistable, and geometrically stretchable organic light-emitting diodes under 2-dimensional random area strain with invariant color coordinates. The devices are fabricated on a thin optical-adhesive/elastomer with a small mechanical bending strain and water-proofed by optical-adhesive encapsulation in a sandwiched structure. The heat dissipation mechanism of the thin optical-adhesive substrate, thin elastomer-based devices or silicon dioxide nanoparticles reduces triplet-triplet annihilation, providing consistent performance at high exciton density, compared with thick elastomer and a glass substrate. The performance is enhanced by the nanoparticles in the optical-adhesive for light out-coupling and improved heat dissipation. A high current efficiency of ~82.4 cd/A and an external quantum efficiency of ~22.3% are achieved with minimum efficiency roll-off.A transparent twistable and stretchable MoO3/Au/MoO3 electrode is demonstrated by Choi et al. for organic light-emitting diodes. The device fabricated on thin elastomer shows enhanced EQE with minimum efficiency roll-off owing to the improved charge injection and heat dissipation from the substrate.
Covalent or Noncovalent? Systematic investigation of polymeric binders incorporating Meldrum's acid reveals most critical binder properties for silicon anodes in lithium ion batteries, that is ...self‐healing effect facilitated by a series of noncovalent interactions.
Intrinsically stretchable organic solar cells (IS‐OSCs) have been recently spotlighted for their omnidirectional stretchability, seamless integrability to any surface, and facile fabrication. Due to ...these attributes, IS‐OSCs are ideal off‐grid power sources, especially for wearable electronics in real‐life. However, under human body elongation as high as ≈40%, cracks in IS‐OSCs are considered inevitable, and the origin of the mechanical failure is rarely identified. Herein, the crack‐initiation and the propagation mechanism are first clarified. Based on this, a crack‐free substrate/transparent electrode platform for stretchable electronics is also suggested. A double‐locking scheme, which reinforces the physical/chemical adsorption within the most mechanically fragile layer, a poly(3,4‐ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and also with thermoplastic polyurethane substrate, is introduced. As a result, the crack‐onset strain of double‐locked IS‐OSCs surpasses 40%, while that of pristine ones is less than 20%. The IS‐OSCs with the double‐locked system exhibits an efficient power conversion efficiency of 10.2%, and the absence of cracks allows the IS‐OSCs to maintain 79.7% of the initial PCE at 40% strain.
The strategies for stretchable “crack‐free” intrinsically stretchable organic solar cells (IS‐OSCs) are proposed. By improving the physical and chemical adhesion between thermoplastic polyurethane substrate and poly(3,4‐ethylene dioxythiophene):poly(styrene sulfonate), crack‐free IS‐OSCs under 40% strain are successfully fabricated and a high power conversion efficiency (PCE) of 10.2% and high stretchability that retain 70% of an initial PCE under 44% strain are demonstrated.
Conjugation of mussel‐inspired catechol groups to various polymer backbones results in materials suitable as silicon anode binders. The unique wetness‐resistant adhesion provided by the catechol ...groups allows the silicon nanoparticle electrodes to maintain their structure throughout the repeated volume expansion and shrinkage during lithiation cycling, thus facilitating substantially improved specific capacities and cycle lives of lithium‐ion batteries.
Owing to their simple chemical structures and straightforward synthesis, poly(thiophene vinylene) (PTV) derivatives are promising types of polymer donors for organic solar cells (OSCs). However, the ...structural rigidity of PTVs results in the formation of films with poor mechanical properties, which limits the application of PTVs in intrinsically stretchable (IS)‐OSCs. Here, new carboxylate‐containing PTVs are developed with tuned molecular weight (MW) (PETTCVT‐X, X = L, M, and H) and realize efficient and mechanically durable IS‐OSCs. The crystallinity of the PTVs increases progressively with increasing MW, leading to enhanced hole mobility and suppressed charge recombination of the OSCs. Moreover, both the mechanical stretchability and electrical properties of the PTVs increase significantly with increasing MW, owing to the formation of tie‐chains that connect the isolated crystalline domains. Consequently, OSCs featuring a PTV with the highest MW (PETTCVT‐H) exhibit the highest power conversion efficiency (PCE, 15.3%) and crack‐onset strain (COS, 7.1%) among the series, compared to lower values for the PETTCVT‐L (PCE = 9.7% and COS = 1.3%) and PETTCVT‐M‐based OSCs (PCE = 12.5% and COS = 3.7%). Therefore, the IS‐OSCs employing PETTCVT‐H present the highest initial PCE (10.1%) and stretchability (strain at PCE80% (retaining 80% of the initial PCE) = 16%).
A series of new carboxylate‐containing poly(thiophene vinylene)s (PETTCVT‐X, X = L, M, and H) with different molecular weights (MWs) is developed. Intrinsically stretchable organic solar cells featuring the highest MW PETTCVT‐H achieve the highest initial power conversion efficiency (PCE= 10.1%) and stretchability (strain at PCE80% = 16%) among the series.
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