The position of the anchoring group is systematically changed with a series of alkyl group wrapped donor–acceptor–donor (D–A–D) based squaraine dyes, 4-SQ to 7-SQ, for the use in dye-sensitized solar cells (DSSCs). By this approach, the orientation as well as the self-assembly of the sensitizers can be controlled on the semiconducting TiO2 surface. All of the dyes functionalized with hydrophobic alkyl groups at sp3-C and N atoms of the indoline units that is far away from the TiO2 surface to control the self-assembly of dyes and passivate the surface. Controlling both the orientation as well as the self-assembly of the sensitizers synergistically enhances the V oc of the DSSC device by imparting the dipole moment on the TiO2 surface and minimizing the interfacial charge recombination process of electrons from TiO2 to the oxidized electrolyte, respectively. Further, the presence of a meta-carboxyl group with respect to the N atom of the indoline donor unit for the dyes 4-SQ and 6-SQ makes them nonconductive for the charge injection process, which sheds light on the importance of through-space electron transfer for the device performance. Emission from the relaxed twisted state was found to be a deactivation pathway for 4-SQ on TiO2 and ZrO2, which revealed the importance of structural factors that promote spatial interaction between the sensitizer and metal oxide surface. Computational studies showed the systematic changes in the dipole moment for the sensitizers 4-SQ, 5-SQ, and 6-SQ upon anchoring to the TiO2 surface. The DSSC device performance varied with the position of anchoring groups in the sensitizers. The DSSC device performance of 5-SQ indicates a J sc value of 11.35 mA cm–2, V oc of 0.698 V, and ff of 77% corresponding to a power conversion efficiency of 6.08% in the presence of 3 equiv of coadsorbent CDCA, which is nearly 1.5 times higher than 6-SQ (V oc 0.7 V, J sc 7.76 mA cm–2, ff 76%, and η 4.14%) and 2.6 times higher than 4-SQ (V oc 0.658 V, J sc 4.42 mA cm–2, ff 78%, and η 2.28%). IPCE studies revealed the importance of orientation for the charge injection and self-assembly of dyes, as devices with 5-SQ and 6-SQ as a sensitizer showed 94 and 77% response at 578 nm, respectively, which correspond to the aggregated structure of the dye. Mott–Schottky and IPCE experiments showed that the orientation of sensitizers could modulate the V oc due to the shift in the flat band potential of TiO2.
P(NDI2OD-T2), also known as Polyera ActivInk N2200, was synthesized by the atom-economic Direct Hetero Arylation Polymerization (DHAP) route using a newly designed A-B-A monomer. The new monomer design involved flanking...
polymeric elastomers are promising materials for the flexible and wearable applications. These conducting elastomers possess an acquiescent nature with human skin that undergoes mechanical deformation while performing physical actions such as stretching, bending, twiddling, and folding. [4,5] The sensitivity over such mechanical strain has been measured by the performance metric like gauge factor (GF) and calculated by measuring the change in resistance (δR) to the external strain (δε). Achieving the high-performing, flexible, and wearable strain sensors by silicon and metal-based systems are ambiguous due to its low GF. [6] It leads to the use of polymeric elastomers to fabricate strain sensors that can mount directly on human skin to sense signals corresponding to human bodily motions. In line with this, numerous materials and methodologies have been reported in developing high-performing strain sensors. The library of conducting filler materials like carbon black, [7,8] CNTs, [9,10] nanoparticles, [11] nanotubes, [12,13] graphene, [14-17] conducting polymers, [18] and hydrogels [19-21] has been used to fabricate strain sensors. Also, the fabrication methods like photolithography, [22] screen printing, [23] inkjet printing, [24,25] and spray coating [26] are employed to develop strain sensors. Though these strain sensors have demonstrated superior performance than that of metal and silicon-based strain gauges, the extension of lab-scale technology to the commercial use is hitherto unrealized due to the complicated pre-treatments, instability, and inadequate sensitivity. More importantly, the realization of a highly conductive and stretchable platform to transduce both the low-and high-strain functions of the human body remains challenging. It means the sensor component must be highly sensitive to detect the subtle involuntary functions such as heartbeat, breathing, and voice recognition that produce ultra-low strains. Contrastingly, the same sensor components should work under high-strain voluntary functions of the human body. To detect these arrays of functions, developing the ideal material/component with a high and broad range of gauge factor (GF) is essential. In general, The wearable strain sensors with multifunctional applications can fuel the rapid development of human-machine intelligence for various sectors like healthcare, soft robotics, and Internet of Things applications. However, achieving the low-cost and mass production of wearable sensors with ultrahigh performance remains challenging. Herein, a simple, cost-effective, and scalable methodology to fabricate the flexible and highly sensitive strain sensors using carbon black and latex rubbers (LR) is presented. The LR-based strain sensor demonstrates excellent flexibility, fast response (≈600 ms), ultra-high sensitivity (maximum gauge factor of 1.2 × 10 4 at 250% strain), and long-term stability over 1000 cycles. The LR-based strain sensors are sensitive to monitor subtle human motions such as heart pulse rate and voice recognition along with high...
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