Layer-by-Layer Assembly of Free-Standing Nanofilms by Controlled Rolling

A water surface not only provides a habitat to many living organisms but also opens up new possibilities to develop state-of-the-art technologies. Here, we show a technology for the layer-by-layer assembly of free-standing nanofilms by controlled rolling. The water surface is exploited as an ideal platform for rolling a nanofilm, allowing adhesion control and frictionless feeding. The nanofilm floating on the water surface is attached to a tube by van der Waals adhesion and is rolled up by the rotation of the tube. This method can assemble diverse film materials including metals, polymers, and two-dimensional materials, with an easy control of the number of layers. Furthermore, heterogeneous and spiral structures of the nanofilm are achieved. Various applications such as a stretchable tubular electrode, an electroactive polymer tube actuator, and a superelastic nanofilm tube are demonstrated. We believe this work can potentially lead to a breakthrough in the nanofilm assembly processes

Layer-by-Layer Assembly of Free-Standing Nanofilms by Controlled Rolling

A water surface not only provides a habitat to many living organisms but also opens up new possibilities to develop state-of-the-art technologies. Here, we show a technology for the layer-by-layer assembly of free-standing nanofilms by controlled rolling. The water surface is exploited as an ideal platform for rolling a nanofilm, allowing adhesion control and frictionless feeding. The nanofilm floating on the water surface is attached to a tube by van der Waals adhesion and is rolled up by the rotation of the tube. This method can assemble diverse film materials including metals, polymers, and two-dimensional materials, with an easy control of the number of layers. Furthermore, heterogeneous and spiral structures of the nanofilm are achieved. Various applications such as a stretchable tubular electrode, an electroactive polymer tube actuator, and a superelastic nanofilm tube are demonstrated. We believe this work can potentially lead to a breakthrough in the nanofilm assembly processes

Layer-by-Layer Assembly of Free-Standing Nanofilms by Controlled Rolling

A water surface not only provides a habitat to many living organisms but also opens up new possibilities to develop state-of-the-art technologies. Here, we show a technology for the layer-by-layer assembly of free-standing nanofilms by controlled rolling. The water surface is exploited as an ideal platform for rolling a nanofilm, allowing adhesion control and frictionless feeding. The nanofilm floating on the water surface is attached to a tube by van der Waals adhesion and is rolled up by the rotation of the tube. This method can assemble diverse film materials including metals, polymers, and two-dimensional materials, with an easy control of the number of layers. Furthermore, heterogeneous and spiral structures of the nanofilm are achieved. Various applications such as a stretchable tubular electrode, an electroactive polymer tube actuator, and a superelastic nanofilm tube are demonstrated. We believe this work can potentially lead to a breakthrough in the nanofilm assembly processes

Layer-by-Layer Assembly of Free-Standing Nanofilms by Controlled Rolling

A water surface not only provides a habitat to many living organisms but also opens up new possibilities to develop state-of-the-art technologies. Here, we show a technology for the layer-by-layer assembly of free-standing nanofilms by controlled rolling. The water surface is exploited as an ideal platform for rolling a nanofilm, allowing adhesion control and frictionless feeding. The nanofilm floating on the water surface is attached to a tube by van der Waals adhesion and is rolled up by the rotation of the tube. This method can assemble diverse film materials including metals, polymers, and two-dimensional materials, with an easy control of the number of layers. Furthermore, heterogeneous and spiral structures of the nanofilm are achieved. Various applications such as a stretchable tubular electrode, an electroactive polymer tube actuator, and a superelastic nanofilm tube are demonstrated. We believe this work can potentially lead to a breakthrough in the nanofilm assembly processes

Layer-by-Layer Assembly of Free-Standing Nanofilms by Controlled Rolling

A water surface not only provides a habitat to many living organisms but also opens up new possibilities to develop state-of-the-art technologies. Here, we show a technology for the layer-by-layer assembly of free-standing nanofilms by controlled rolling. The water surface is exploited as an ideal platform for rolling a nanofilm, allowing adhesion control and frictionless feeding. The nanofilm floating on the water surface is attached to a tube by van der Waals adhesion and is rolled up by the rotation of the tube. This method can assemble diverse film materials including metals, polymers, and two-dimensional materials, with an easy control of the number of layers. Furthermore, heterogeneous and spiral structures of the nanofilm are achieved. Various applications such as a stretchable tubular electrode, an electroactive polymer tube actuator, and a superelastic nanofilm tube are demonstrated. We believe this work can potentially lead to a breakthrough in the nanofilm assembly processes

Simultaneously Enhancing the Cohesion and Electrical Conductivity of PEDOT:PSS Conductive Polymer Films using DMSO Additives

Conductive polymer poly­(3,4-ethylene­dioxy­thiophene):­poly­(styrene­sulfonate) (PEDOT:PSS) has attracted significant attention as a hole transport and electrode layer that substitutes metal electrodes in flexible organic devices. However, its weak cohesion critically limits the reliable integration of PEDOT:PSS in flexible electronics, which highlights the importance of further investigation of the cohesion of PEDOT:PSS. Furthermore, the electrical conductivity of PEDOT:PSS is insufficient for high current-carrying devices such as organic photovoltaics (OPVs) and organic light emitting diodes (OLEDs). In this study, we improve the cohesion and electrical conductivity through adding dimethyl sulfoxide (DMSO), and we demonstrate the significant changes in the properties that are dependent on the wt % of DMSO. In particular, with the addition of 3 wt % DMSO, the maximum enhancements for cohesion and electrical conductivity are observed where the values increase by 470% and 6050%, respectively, due to the inter-PEDOT bridging mechanism. Furthermore, when OLED devices using the PEDOT:PSS films are fabricated using the 3 wt % DMSO, the display exhibits 18% increased current efficiency

Cooptimization of Adhesion and Power Conversion Efficiency of Organic Solar Cells by Controlling Surface Energy of Buffer Layers

Here, we demonstrate the cooptimization of the interfacial fracture energy and power conversion efficiency (PCE) of poly­[<i>N</i>-9′-heptadecanyl-2,7-carbazole-<i>alt</i>-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT)-based organic solar cells (OSCs) by surface treatments of the buffer layer. The investigated surface treatments of the buffer layer simultaneously changed the crack path and interfacial fracture energy of OSCs under mechanical stress and the work function of the buffer layer. To investigate the effects of surface treatments, the work of adhesion values were calculated and matched with the experimental results based on the Owens–Wendt model. Subsequently, we fabricated OSCs on surface-treated buffer layers. In particular, ZnO layers treated with poly­[(9,9-bis­(3′-(<i>N</i>,<i>N</i>-dimethyl­amino)­propyl)-2,7-fluorene)-<i>alt</i>-2,7-(9,9-dioctylfluorene)] (PFN) simultaneously satisfied the high mechanical reliability and PCE of OSCs by achieving high work of adhesion and optimized work function

Accelerated Degradation Due to Weakened Adhesion from Li-TFSI Additives in Perovskite Solar Cells

Reliable integration of organometallic halide perovskite in photovoltaic devices is critically limited by its low stability in humid environments. Furthermore, additives to increase the mobility in the hole transport material (HTM) have deliquescence and hygroscopic properties, which attract water molecules and result in accelerated degradation of the perovskite devices. In this study, a double cantilever beam (DCB) test is used to investigate the effects of additives in the HTM layer on the perovskite layer through neatly delaminating the interface between the perovskite and HTM layers. Using the DCB test, the bottom surface of the HTM layers is directly observed, and it is found that the additives are accumulated at the bottom along the thickness (i.e., through-plane direction) of the films. It is also found that the additives significantly decrease the adhesion at the interface between the perovskite and HTM layers by more than 60% through hardening the HTM films. Finally, the adhesion-based degradation mechanism of perovskite devices according to the existence of additives is proposed for humid environments

N‑Containing 1,7-Octadiyne Derivatives for Living Cyclopolymerization Using Grubbs Catalysts

Synthesis of a new class of conjugated polyenes containing N-heterocyclic six-membered rings was demonstrated via cyclopolymerization of N-containing 1,7-octadiyne derivatives using Grubbs catalysts. Successful cyclopolymerization was achieved by introducing protecting groups to the amines in the monomers. Moreover, a hydrazide-type monomer containing a di-<i>tert</i>-butyloxycarbonyl group (<b>6</b>) promoted the living cyclopolymerization to give poly­(<b>6</b>) with a controlled molecular weight and narrow dispersity. This living polymerization allowed us to prepare various conjugated diblock copolymers using poly­(<b>6</b>) as the first block

Mechanical Properties of Polymer–Fullerene Bulk Heterojunction Films: Role of Nanomorphology of Composite Films

This paper reports the tensile properties and fracture mechanism of PTB7:PC₇₁BM bulk heterojunction (BHJ) films as a function of composition mixing ratio. An increased concentration of fullerene makes the BHJ films stiffer and more brittle, and fracture occurs along aggregated fullerene domain boundaries. The tensile strength is maximized at a polymer–fullerene content ratio of 1:1. Furthermore, an additive, 1,8-diiodoctane (DIO), in the films induces fine nanomorphology, which increases the stiffness and strength and reduces the ductility of the films further. This is especially true under a high PC₇₁BM load due to the expanded interfacial surface areas between the PC₇₁BM and PTB7 polymer domains. The photovoltaic performance of the BHJ films on polydimethylsiloxane (PDMS) substrates after tensile stretching cycles is also examined in detail