top of page

Shared Interests Group

Public·11 members

Design Design 2019 V2.1 Crack [Extra Quality]

As a key component in stretchable electronics, semiconducting polymers have been widely studied. However, it remains challenging to achieve stretchable semiconducting polymers with high mobility and mechanical reversibility against repeated mechanical stress. Here, we report a simple and universal strategy to realize intrinsically stretchable semiconducting polymers with controlled multi-scale ordering to address this challenge. Specifically, incorporating two types of randomly distributed co-monomer units reduces overall crystallinity and longer-range orders while maintaining short-range ordered aggregates. The resulting polymers maintain high mobility while having much improved stretchability and mechanical reversibility compared with the regular polymer structure with only one type of co-monomer units. Interestingly, the crystalline microstructures are mostly retained even under strain, which may contribute to the improved robustness of our stretchable semiconductors. The proposed molecular design concept is observed to improve the mechanical properties of various p- and n-type conjugated polymers, thus showing the general applicability of our approach. Finally, fully stretchable transistors fabricated with our newly designed stretchable semiconductors exhibit the highest and most stable mobility retention capability under repeated strains of 1,000 cycles. Our general molecular engineering strategy offers a rapid way to develop high mobility stretchable semiconducting polymers.

Design Design 2019 V2.1 Crack

With increasing needs for wearable and implantable electronics, flexible and stretchable electronics have developed recently1,2,3,4,5,6,7,8,9. Such electronics with new form factors will undoubtedly improve our daily life in the future10. A number of promising applications, such as stretchable circuits11,12,13,14,15,16, displays17,18,19,20,21,22, and energy storage devices23,24,25,26,27, have been demonstrated. As a key component in electronics, semiconductors that are intrinsically stretchable will allow the fabrication of high-density devices and create more robust products. Stretchable semiconducting polymers have several additional advantages such as low-cost solution processability and scalability28,29; however, several challenges remain to be overcome for stretchable semiconducting polymers. For example, charge carrier mobility is often reduced with increasing stretchability, which significantly limits the use of stretchable semiconducting polymers30,31. Even though significant progress has been made with the incorporation of dynamic bonding units, partial breakage of the conjugation makes it challenging to control the morphology, which makes it difficult to realize high mobility32,33,34. Several types of additives have been reported and have shown some promise. However, such multi-component systems are highly sensitive to processing conditions35,36,37. In some approaches, specific molecular combinations are required to achieve high stretchability38, which may limit the broad application of such methods. Therefore, it is desired to develop a molecular design strategy that is easy to access, reliable without phase-separation, generally applicable to a variety of known high-mobility polymer semiconductors, and offers high stretchability without compromising charge carrier mobility.

Herein, we report a simple and general molecular design strategy for high-mobility intrinsically stretchable polymer semiconductors to address the above limitations. Specifically, stretchable terpolymer-based (comprising three discrete conjugated building blocks) semiconductors were synthesized by utilizing various fractions of two types of constituting co-monomers. The afforded semiconducting terpolymers are found to be stretchable to >100% strain without crack formation. As no additives are needed to tune the mechanical properties, these polymers readily give high mobilities and high stretchability. The molecular design concept is found to be generally applicable and thus allows the rapid development of a variety of stretchable p-type and n-type semiconductors. We hypothesized that the introduction of two different types of fully conjugated co-monomers may not significantly affect the short-range aggregation of polymeric chains, whereas the structural randomness of the backbone may hinder the formation of larger crystalline domains, which tend to fracture upon strain39. This controlled ordering at different length scales may improve stretchability without compromise of charge transport.

In our molecular design, we hypothesized that the use of structurally similar co-monomers may be essential to maintain short-range aggregation. If the co-monomers are significantly different, then the short-range aggregation may be disrupted, which may result in reduced mobility. For example, Lin et al.40 reported significant decrease in mobility was observed in terpolymer semiconductors, when the polymers were prepared with dissimilar co-monomers. As TVT and BT have similar structures, such mobility compromise may be avoided in our terpolymers.

To understand the mechanisms of our terpolymer design achieving both high mobility and great mechanical properties, we first performed AFM to characterize the surface morphology of the polymer thin films. We observed that our terpolymers have fiber-like morphology, which is commonly observed for such conjugated polymers42 (Supplementary Fig. 20). Next, ultraviolet-visible/near-infrared (UV-Vis/NIR) spectroscopy was performed to understand the intermolecular aggregation of the terpolymers. As conjugated polymer semiconductors often form aggregates, comparing the intensity of 0-1 and 0-0 vibronic peaks can offer information regarding the relative degree of aggregation43,44. In both solution and thin-film states, negligible change of relative degree of aggregation was observed from DPP-0TVT to DPP-10TVT (Fig. 2a and Supplementary Fig. 21), which confirmed our hypothesis that the terpolymers are able to maintain local short-range aggregates. As aggregation is essential for efficient inter-chain charge transport, the obtained results explained the relatively unchanged mobilities of our terpolymers. The activation energy for charge transport was extracted from temperature-dependent electrical measurements using the Arrhenius equation45. DPP-8TVT showed similar charge transport activation energy, suggesting no change in trap states compared to other polymers (Fig. 2b and Supplementary Fig. 22).

To understand how microstructures of the polymer thin films are affected by the terpolymer design, we performed grazing incidence X-ray diffraction (GIXD). Interestingly, the diffraction intensity of the terpolymers was significantly lower than that of the reference copolymers (DPP-0TVT and 10TVT) (Fig. 2d and Supplementary Fig. 24). The relative degree of crystallinity (rDoC) of the films was calculated based on (2 0 0) diffraction peak intensity. Consistent with the DSC data, the terpolymers showed clearly lower rDoC than the regular copolymers DPP-0TVT or DPP-10TVT (Fig. 2e, f). This result confirms our hypothesis that the structural randomness of the terpolymers may decrease the crystallinity, i.e., the longer-range order39. Interestingly, DPP-8TVT showed the lowest crystallinity, although it contains the rigid unit (TVT) more than other terpolymers (DPP-2TVT and 5TVT). The backbone conformation of the terpolymers may be highly disrupted, as the two different co-monomers are randomly incorporated. In this case, the more flexible unit (BT) may be able to easily fill in the structural defects to form ordered domains, whereas the more rigid unit (TVT) may not.

Another important parameter is the glass transition temperature (Tg) of the terpolymers, as dynamic behaviors of the polymeric chains may affect the microstructures and the properties. In our terpolymer design, we expected that the difference in Tg may be negligible, given the structural similarity of the co-monomers used to construct the terpolymers (Supplementary Fig. 25). Therefore, the improved stretchability might not originate from the enhanced dynamic behaviors of the polymeric chains, but from the controlled multi-scale ordering.

All of the above results indicate that our terpolymers possess all of the three desired properties (high mobility, stretchability, and mechanical reversibility) as stretchable polymer semiconductors. Importantly, the terpolymer design has significantly improved reliability, compared with previously reported multi-component stretchable semiconductor films with elastomers or molecular additives. Specifically, significant sample-to-sample variations occur when the second component is introduced, depending on the choice of the second component, its fraction, and processing conditions, which limits the applications of such approaches36,37. However, our terpolymers exhibited significantly improved stretchability without any compromise of mobility, regardless of processing conditions (Supplementary Fig. 10) and molecular components (Figs. 1 and 4). In addition, our terpolymer-based stretchable semiconductors are easily achievable with simples synthesis, which distinguishes this work from literature reported approaches that require additional synthetic steps32,33.

In conclusion, we have successfully developed terpolymer-based stretchable polymer semiconductors. Our described molecular design is readily achievable with various monomers and therefore the stretchable polymer semiconductors are easily synthesized. The newly designed terpolymer semiconductors show high stretchability and mechanical reversibility, while retaining high charge carrier mobility even after repeated strain. Through the detailed characterization experiments, it was shown that the terpolymers maintained short-range aggregations with reduced overall crystallinity and average crystalline domain sizes. Furthermore, a series of intrinsically stretchable semiconductors, including several p- and n-type structures, were demonstrated using our molecular design concept. The fully stretchable transistors fabricated with our terpolymer films do not suffer from performance degradation even after being subjected to repeated or various types of mechanical deformations. To the best of our knowledge, the fabricated stretchable transistors exhibited one of the highest mobilities under repeated strain. With fine-tuning of additional molecular parameters, such as monomer choice, fraction, and backbone sequence, we believe terpolymer-based semiconductors can be further improved, providing a promising path towards high-performance stretchable polymer semiconductors.

  • About

    Welcome to the group! You can connect with other members, ge...

    Group Page: Groups_SingleGroup
    bottom of page