Liang Huang

Quinoxaline-containing poly(4,5-ethylene-2,7-carbazole) (PECz-DTQx) shows a high efficiency of 6.07% in solar cells with a PFN/Al bilayer cathode. This is higher than the efficiency achieved with sole Al (3.99%) or with Ca/Al (4.52%) cathodes. A bilayer cathode could be valuable in device configurations to achieve high efficiency in combination with a high-performance polymer donor. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Three benzotriazole (BTA)-based conjugated polymers PF-DTBTA, PCz-DTBTA, and PPh-DTBTA, with electron-donating segments of fluorene, carbazole, and dialkoxybenzene, respectively, were successfully synthesized as new polymeric donors in bulk-heterojunction (BHJ) photovoltaic cells (PVCs). All the copolymers exhibited good solubility in common organic solvents and good thermal stability. The optical band gaps for PF-DTBTA, PCz-DTBTA, and PPh-DTBTA are 2.24, 2.18, and 1.87 eV, respectively. The HOMO levels for PF-DTBTA, PCz-DTBTA, and PPh-DTBTA are −5.67, −5.54, and −5.20 eV, respectively, which were determined by the electron-donating segments. The LUMO levels for PF-DTBTA, PCz-DTBTA, and PPh-DTBTA are −3.43, −3.36, and −3.33 eV, respectively, which were mainly dominated by the BTA unit. For a blend ratio of polymer:PCBM = 1:2, BHJ PVCs with Al cathode displayed power conversion efficiencies (PCE) of 0.9%, 1.51%, and 1.16% for PF-DTBTA, PCz-DTBTA, and PPh-DTBTA, respectively. Alcohol-soluble poly[(9,9-dioctyl-2,7-fluorene)-alt-(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)] (PFN) was selected for cathode modification. For BHJ PVCs with PF-DTBTA and PCz-DTBTA as the donors, open-circuit voltages (Voc) of the PVCs could all be elevated with the PFN/Al bilayer cathode, whereas no such improvements were found for PVCs with PPh-DTBTA as the donor. The behaviors could be attributed to the different Voc losses when using Al cathode. Using PFN/Al bilayer cathode could also improve short-curcuit current and fill factor for the three BTA-based copolymers. The N−N interactions between the BTA-based polymers and the PFN may modify interfacial contact, resulting in enhancement of the electron extraction from the acceptor phase to the cathode and decreasing hole−electron recombination in the active layer. Consequently, PFN/Al bilayer cathode elevated PCE values to 1.3%, 2.75%, and 1.39% for PF-DTBTA, PCz-DTBTA, and PPh-DTBTA, respectively. The most significant increasing of PCE with a calculated value of 80% was found for PCz-DTBTA as the donor, and this might be related to the additional N−N interactions between the carbazole segments and the PFN. The results would supply useful information to understand the contribution of an interfacial layer on the photovoltaic performance. Our results also suggest that the bilayer cathode would have great potential to elevate PCE of BHJ PVCs.

Recent advances in lab-on-a-chip technology establish solid foundations for wearable biosensors. These newly emerging wearable biosensors are capable of non-invasive, continuous monitoring by miniaturization of electronics and integration with microfluidics. The advent of flexible electronics, biochemical sensors, soft microfluidics, and pain-free microneedles have created new generations of wearable biosensors that explore brand-new avenues to interface with the human epidermis for monitoring physiological status. However, these devices are relatively underexplored for sports monitoring and analytics, which may be largely facilitated by the recent emergence of wearable biosensors characterized by real-time, non-invasive, and non-irritating sensing capacities. Here, we present a systematic review of wearable biosensing technologies with a focus on materials and fabrication strategies, sampling modalities, sensing modalities, as well as key analytes and wearable biosensing platforms for healthcare and sports monitoring with an emphasis on sweat and interstitial fluid biosensing. This review concludes with a summary of unresolved challenges and opportunities for future researchers interested in these technologies. With an in-depth understanding of the state-of-the-art wearable biosensing technologies, wearable biosensors for sports analytics would have a significant impact on the rapidly growing field-microfluidics for biosensing.