Fluorinated Benzothiadiazole (BT) Groups as a Powerful Unit for High-Performance Electron-Transporting Polymers

Over the past few years, one of the most remarkable advances in the field of polymer solar cells (PSCs) has been the development of fluorinated 2,1,3-benzothiadiazole (BT)-based polymers that lack the solid working principles of previous designs, but boost the power conversion efficiency. To assess a rich data set for the influence of the fluorinated BT units on the charge-transport characteristics in organic field-effect transistors (OFETs), we synthesized two new polymers (<b>PDPP-FBT</b> and <b>PDPP-2FBT</b>) incorporating diketopyrrolopyrrole (DPP) and either single- or double-fluorinated BT and thoroughly investigated them via a range of techniques. Unlike the small differences in the absorption properties of <b>PDPP-FBT</b> and its nonfluorinated analogue (<b>PDPP-BT</b>), the introduction of doubly fluorinated BT into the polymer backbone induces a noticeable change in its optical profiles and energy levels, which results in a slightly wider bandgap and deeper HOMO for <b>PDPP-2FBT</b>, relative to the others. Grazing incidence X-ray diffraction (GIXD) analysis reveals that both fluorinated polymer films have long-range orders along the out-of-plane direction, and π–π stacking in the in-plane direction, implying semicrystalline lamellar structures with edge-on orientations in the solid state. Thanks to the strong intermolecular interactions and highly electron-deficient π-systems driven by the inclusion of F atoms, the polymers exhibit electron mobilities of up to 0.42 and 0.30 cm² V^–1 s^–1 for <b>PDPP-FBT</b> and <b>PDPP-2FBT</b>, respectively, while maintaining hole mobilities higher than 0.1 cm² V^–1 s^–1. Our results highlight that the use of fluorinated BT blocks in the polymers is a promising molecular design strategy for improving electron transporting performance without sacrificing their original hole mobility values

Highs and lows of lambing time: Sheep farmers? perceptions of the first outbreak of schmallenberg disease in south west England on their well-being

The outbreak of a previously unknown and new disease in the United Kingdom, known as ‘Schmallenberg disease’, a disease associated with abortions, stillbirths and fetal deformities in naïve ewes, was reported for the first time in South West England during the 2012/13 early lambing season. Epidemiological studies confirmed that the Schmallenberg virus (SBV) had a severe negative impact upon animal welfare and the productivity of affected flocks. By contrast, there was a specific lack of research on the impact of SBV on sheep farmer well-being. This study aimed to improve our understanding of sheep farmers’ experiences of Schmallenberg disease, and the impact of the first outbreak on sheep farmer well-being during the 2012/13 early lambing season in South West England. Face-to-face, semi-structured interviews with six farmers with small flocks of pedigree and purebred sheep in South West England were conducted in 2013. The data were analysed via thematic analysis. The main themes regarding the impact of disease on farmer well-being included: (i) emotional highs and lows are part of a normal lambing season; (ii) negative emotions and memories associated with the Schmallenberg disease outbreak; and (iii) resilience and coping with the unexpected disease outbreak. These novel data present preliminary findings from a small number of sheep farmers, and indicate that for some farmers, an unexpected outbreak of a new and emerging disease for the first time during lambing, and dealing with high levels of dystocia, deformities and deaths in their animals, had a negative impact on their emotional well-being during the peak period of the sheep production cycle

Synthesis of PCDTBT-Based Fluorinated Polymers for High Open-Circuit Voltage in Organic Photovoltaics: Towards an Understanding of Relationships between Polymer Energy Levels Engineering and Ideal Morphology Control

The introduction of fluorine (F) atoms onto conjugated polymer backbone has verified to be an effective way to enhance the overall performance of polymer-based bulk-heterojunction (BHJ) solar cells, but the underlying working principles are not yet fully uncovered. As our attempt to further understand the impact of F, herein we have reported two novel fluorinated analogues of PCDTBT, namely, <b>PCDTFBT</b> (1F) and <b>PCDT2FBT</b> (2F), through inclusion of either one or two F atoms into the benzothiadiazole (BT) unit of the polymer backbone and the characterization of their physical properties, especially their performance in solar cells. Together with a profound effect of fluorination on the optical property, nature of charge transport, and molecular organization, F atoms are effective in lowering both the HOMO and LUMO levels of the polymers without a large change in the energy bandgaps. <b>PCDTFBT</b>-based BHJ solar cell shows a power conversion efficiency (PCE) of 3.96 % with high open-circuit voltage (<i>V</i>_OC) of 0.95 V, mainly due to the deep HOMO level (−5.54 eV). To the best of our knowledge, the resulting <i>V</i>_OC is comparable to the record <i>V</i>_OC values in single junction devices. Furthermore, to our delight, the best <b>PCDTFBT</b>-based device, prepared using 2 % v/v diphenyl ether (DPE) additive, reaches the PCE of 4.29 %. On the other hand, doubly-fluorinated polymer <b>PCDT2FBT</b> shows the only moderate PCE of 2.07 % with a decrease in <i>V</i>_OC (0.88 V), in spite of the further lowering of the HOMO level (−5.67 eV) with raising the number of F atoms. Thus, our results highlight that an improvement in efficiency by tuning the energy levels of the polymers by means of molecular design can be expected only if their truly optimized morphologies with fullerene in BHJ systems are materialized