2,2′,7,7′-Tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD), the prevalent organic hole transport material used in solid-state dye-sensitized solar cells and ...perovskite-absorber solar cells, relies on an uncontrolled oxidative process to reach appreciable conductivity. This work presents the use of a dicationic salt of spiro-OMeTAD, named spiro(TFSI)2, as a facile means of controllably increasing the conductivity of spiro-OMeTAD up to 10–3 S cm–1 without relying on oxidation in air. Spiro(TFSI)2 enables the first demonstration of solid-state dye-sensitized solar cells fabricated and operated with the complete exclusion of oxygen after deposition of the sensitizer with higher and more reproducible device performance. Perovskite-absorber solar cells fabricated with spiro(TFSI)2 show improved operating stability in an inert atmosphere. Gaining control of the conductivity of the HTM in both dye-sensitized and perovskite-absorber solar cells in an inert atmosphere using spiro(TFSI)2 is an important step toward the commercialization of these technologies.
Fullerene dimerization has been linked to short circuit current (J sub(sc)) losses in organic solar cells comprised of certain polymer-fullerene systems. We investigate several polymer-fullerene ...systems, which present J sub(sc) loss to varying degrees, in order to determine under which conditions dimerization occurs. By reintroducing dimers into fresh devices, we confirm that the photo-induced dimers are indeed the origin of the J sub(sc) loss. We find that both film morphology and electrical bias affect the photodimerization process and thus the associated loss of J sub(sc). In plain fullerene films, a higher degree of crystallinity can inhibit the dimerization reaction, as observed by high performance liquid chromatography (HPLC) measurements. In blend films, the amount of dimerization depends on the degree of mixing between polymer and fullerene. For highly mixed systems with very amorphous polymers, no dimerization is observed. In solar cells with pure polymer and fullerene domains, we tune the fullerene morphology from amorphous to crystalline by thermal annealing. Similar to neat fullerene films, we observe improved light stability for devices with crystalline fullerene domains. Changing the operating conditions of the investigated solar cells from V sub(oc) to J sub(sc) also significantly reduces the amount of dimerization-related J sub(sc) loss; HPLC analysis of the active layer shows that more dimers are formed if the cell is held at V sub(oc) instead of J sub(sc). The effect of bias on dimerization, as well as a clear correlation between PL quenching and reduced dimerization upon addition of small amounts of an amorphous polymer into PC60BM films, suggests a reaction mechanism viaexcitons.
A semiconductor that can be processed on a large scale with a bandgap around 1.8 eV could enable the manufacture of highly efficient low cost double-junction solar cells on crystalline Si. ...Solution-processable organic–inorganic halide perovskites have recently generated considerable excitement as absorbers in single-junction solar cells, and though it is possible to tune the bandgap of (CH3NH3)Pb(Br x I1–x )3 between 2.3 and 1.6 eV by controlling the halide concentration, optical instability due to photoinduced phase segregation limits the voltage that can be extracted from compositions with appropriate bandgaps for tandem applications. Moreover, these materials have been shown to suffer from thermal degradation at temperatures within the processing and operational window. By replacing the volatile methylammonium cation with cesium, it is possible to synthesize a mixed halide absorber material with improved optical and thermal stability, a stabilized photoconversion efficiency of 6.5%, and a bandgap of 1.9 eV.
A promising approach for upgrading the performance of an established low-bandgap solar technology without adding much cost is to deposit a high bandgap polycrystalline semiconductor on top to make a ...tandem solar cell. We use a transparent silver nanowire electrode on perovskite solar cells to achieve a semi-transparent device. We place the semi-transparent cell in a mechanically-stacked tandem configuration onto copper indium gallium diselenide (CIGS) and low-quality multicrystalline silicon (Si) to achieve solid-state polycrystalline tandem solar cells with a net improvement in efficiency over the bottom cell alone. This work paves the way for integrating perovskites into a low-cost and high-efficiency (>25%) tandem cell.
The dissociation constants (pKa) of the eight amines, namely, N‐(2‐aminoethyl)‐1,3‐propanediamine, 2‐methylpentamethylene diamine, N,N‐dimethyldipropylene‐triamine, ...3,3′‐diamino‐N‐methyl‐dipropylamine, Bis2‐(N,N‐dimethylamino) ethylether, 2‐2‐(dimethyl‐amino)ethoxy ethanol, 2‐(dibutylamino) ethanol, and N‐propylethanolamine were measured between 298.15 and 313.15 K with 5 K increment. Based on the experimental values and using the van't Hoff equation, thermodynamic properties such as the standard state changes of enthalpy, entropy, and Gibbs free energy were calculated. Using computational chemistry calculations, the amine that is protonated first was predicted. Furthermore, computer‐free group contribution methods such as the original Perrin–Dempsey–Serjeant (PDS), the modified PDS, and the Qian–Sun–Sun–Gao (QSSG) model were used to estimate the dissociation constants of the studied amines at 298.15 K. The QSSG provided the most accurate results. Finally, this work utilized an artificial neural network for estimating the pKa values, which were in excellent agreement with the experimental data.
Few studies have examined the self-perceptions of autistic adults. This study aimed firstly to investigate domain-specific self-concepts and global self-esteem in autistic adults. The second aim was ...to examine associations between autism self-appraisals, perceived social support and global self-concept and self-esteem. The third was to determine which domains of self-concept were most closely associated with self-esteem. Participants included 71 autistic adults aged 18–70 years and 65 age, sex and education matched typically developing individuals. Participants completed an online survey of autism characteristics, global self-esteem and domain-specific self-concepts (i.e. likeability, task accomplishment, power, giftedness, invulnerability, and morality), self-appraisals about autism, and perceived social support. Autistic participants reported significantly lower power and global self-esteem than typically developing individuals after controlling for autism characteristics. More positive self-appraisals about autism (i.e. greater perceived benefits and lower helplessness) were significantly related to better global self-concept and self-esteem. Global self-esteem was significantly and positively associated with perceptions of giftedness, emotional resilience and power. These findings suggest that autistic adults may perceive themselves as having a low sense of power in their relationships and have negative global perceptions of their self-worth. However, those able to find positive meaning or benefits associated with autism are likely to have more positive global self-perceptions. This study provides new insights into how autistic adults perceive themselves which may guide the focus of psychosocial interventions that seek to recognize and promote unique talents and emotional resilience.
Radon (222Rn) is a widely used tracer in groundwater and surface water studies. In some applications of radon, samples need to be collected from deep submerged areas or discharge points such as caves ...or springs, locations typically accessed by scuba diving. However, there are no established sampling methods for collecting water by scuba diving for Rn analysis. We assessed four underwater sample collection methods: (a) injection into a catheter bag followed by transfer to a bottle after the dive, (b) air purging and then filling of a bottle by allowing gas to escape, (c) air purging followed by gas escape, and then overfilling of water with a syringe, and (d) collection with a syringe followed by transfer to a bottle. The samples were collected from the anchialine caves of the Yucatan Peninsula which are the longest underwater cave systems. The samples were analyzed using the same Rn‐in‐air analyzer and protocols. Statistical comparison of sampling at the same location with different methods showed no significant differences in Rn activity. No collection method is superior in terms of measurement quality; operational simplicity is thus preferred. Statistically significant differences in activity were observed between fresh and saline samples from the same cave, with higher activities in the fresh samples, regardless of sampling method. The saline groundwater therefore has a lower residence time, suggesting vigorous landwards flow. Our assessment shows that in situ sampling of discrete water samples for Rn tracing by divers is a useful and powerful approach allowing the study of otherwise impossible sites.
Key Points
Different underwater sample collection methods by scuba divers for Rn‐in‐water was assessed
All four tested methods showed no differences in measured Rn activity
Radon is higher in saline groundwater versus fresh water in anchialine submerged caves of the Yucatan Peninsula
Eosinophils are traditionally associated with allergic and parasitic inflammation. More recently, eosinophils have also been shown to have roles in diverse processes including development, intestinal ...health, thymic selection, and B‐cell survival with the majority of these insights being derived from murine models and in vitro assays. Despite this, tools to measure the dynamic activity of eosinophils in situ have been lacking. Intravital microscopy is a powerful tool that enables direct visualization of leukocytes and their dynamic behavior in real‐time in a wide range of processes in both health and disease. Until recently eosinophil researchers have not been able to take full advantage of this technology due to a lack of tools such as genetically encoded reporter mice. This mini‐review examines the history of intravital microscopy with a focus on eosinophils. The development and use of eosinophil‐specific Cre (EoCre) mice to create GFP and tdTomato fluorescent reporter animals is also described. Genetically encoded eosinophil reporter mice combined with intravital microscopy provide a powerful tool to add to the toolbox of technologies that will help us unravel the mysteries still surrounding this cell.
Genetically encoded eosinophil reporter mice combined with intravital microscopy provide a powerful tool to help answer questions about eosinophil behavior in health and disease.
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