Financial Analysis of Otter Tail Corporation

Otter Tail is a holding company with 5 subsidiaries residing in three different business segments: electric, which includes the production, transmission, distribution and sale of electric energy; manufacturing, which consists of businesses in the manufacturing contract machining, metal parts stamping, fabrication and painting, and production of material and handling trays and horticultural containers; and plastics, which consists of businesses producing polyvinyl chloride pipe. The electric segment provided electricity to more than 130,000 customers in western Minnesota, eastern North Dakota and northeastern South Dakota. The investment recommendation given in this report was based on a Corporate Valuation Model that discounts free cash flows at the Weighted Average Cost of Capital (WACC)

Triplet Formation in a 9,10-Bis(phenylethynyl)anthracene Dimer and Trimer Occurs by Charge Recombination Rather than Singlet Fission

We present an experimental study investigating the solvent-dependent dynamics of a 9,10-bis(phenylethynyl)anthracene monomer, dimer, and trimer. Using transient absorption spectroscopy, we have discovered that triplet excited state formation in the dimer and trimer molecules in polar solvents is a consequence of charge recombination subsequent to symmetry-breaking charge separation rather than singlet fission. Total internal reflection emission measurements of the monomer demonstrate that excimer formation serves as the primary decay pathway at a high concentration. In the case of highly concentrated solutions of the trimer, we observe evidence of triplet formation without the prior formation of a charge-separated state. We postulate that this is attributed to the formation of small aggregates, suggesting that oligomers mimicking the larger chromophore counts in crystals could potentially facilitate singlet fission. Our experimental study sheds light on the intricate dynamics of the 9,10-bis(phenylethynyl)anthracene system, elucidating the role of solvent- and concentration-dependent factors for triplet formation and charge separation

π-Conjugation and End Group Effects in Long Cumulenes: Raman Spectroscopy and DFT Calculations

We have investigated the structure and spectroscopic properties of cumulenic carbon chains, focusing on the peculiar π-conjugation properties and end-group effects that influence their behavior. With support from Density Functional Theory (DFT) calculations, we have analyzed the IR and Raman spectra of cumulenes characterized by different end-capping groups and we have related them to the bond length alternation (BLA) pattern and local spectroscopic parameters associated with the CC bonds along the sp-carbon chain. For cumulenes we observe a breakdown of the correlation existing in polyynes among frequencies, Raman intensities of the Ʀ line (longitudinal CC stretching modes), and BLA. While the low Ʀ line frequency and equalized CC bonds would indicate the “metallic” character of cumulenic species, we obtain an unusually strong Raman intensity, which is typical of bond-alternated (semiconductive) structures. DFT calculations reveal that this is a consequence of π-electron conjugation, which markedly extends from the sp-carbon chain to the aryl rings belonging to the end groups. These findings suggest the existence of a strong electronic, vibrational and structural coupling between sp-carbon chains and sp2-carbon species, which could play a key role in nanostructured sp/sp2-hybrid carbon materials (e.g., linear carbon chains coupled to graphene domains). Within this context, Raman spectroscopy is a valuable tool for the detailed characterization of the molecular properties of this kind of materials

Molecular rotational conformation controls the rate of singlet fission and triplet decay in pentacene dimers

Three pentacene dimers have been synthesized to investigate the effect of molecular rotation and rotational conformations on singlet fission (SF). In all three dimers, the pentacene units are linked by a 1,4-diethynylphenylene spacer that provides almost unimpeded rotational freedom between the pentacene- and phenylene-subunits in the parent dimer. Substituents on the phenylene spacer add varying degrees of steric hindrance that restricts both the rotation and the equilibrium distribution of different conformers; the less restricted conformers exhibit faster SF and more rapid subsequent triplet-pair recombination. Furthermore, the rotational conformers have small shifts in their absorption spectra and this feature has been used to selectively excite different conformers and study the resulting SF. Femtosecond transient absorption studies at 100 K reveal that the same dimer can have orders of magnitude faster SF in a strongly coupled conformer compared to a more weakly coupled one. Measurements in polystyrene further show that the SF rate is nearly independent of viscosity whereas the triplet pair lifetime is considerably longer in a high viscosity medium. The results provide insight into design criteria for maintaining high initial SF rate while suppressing triplet recombination in intramolecular singlet fission

Förster Resonance Energy Transfer Sensitized Singlet Fission in BODIPY-Pentacene Dimer Conjugates

In the present work, the energy donor 4,4-difluoro-4-bora-3a,4a-diaza-sindacene (BODIPY) is used for the first time in combination with a pentacene dimer (Pnc2) to provide the conjugate BODIPYPnc2 that features absorption throughout a large part of the solar spectrum. Upon photoexcitation, the singlet excited state energy of BODIPY is transferred to the pentacene dimer via intramolecular Förster resonance energy transfer (FRET). Subsequently, the pentacene dimer undergoes intramolecular singlet fission. In this process, a singlet correlated triplet pair is generated from the first singlet excited state via coupling to an intermediate state. The results show that solvent polarity has an influence on the system, with the largest FRET rate (i.e., 7.46 × 1011 s−1) being obtained in the most polar solvent (namely, benzonitrile) along with the largest triplet quantum yield (i.e., 207 ± 20%)A.-S.W., G.L., and I.P. contributed equally to this work. D.M.G. thanks the financial support from ″the German Research Foundation (DFG) via SFB 953 “Synthetic Carbon Allotropes” and “Solar Technologies go Hybrid (SolTech)” Initiative of the Bavarian Ministry for Science. T.T. acknowledges financial support from MICINN (PID2020-116490GB-I00 and TED2021-131255B-C43), the Comunidad de Madrid and the Spanish State through the Recovery, Transformation and Resilience Plan [“Materiales Disruptivos Bidimensionales (2D)” (MAD2D-CM) (UAM1)-MRR Materiales Avanzados], and the European Union through the Next Generation EU funds. IMDEA Nanociencia acknowledges support from the “Severo Ochoa” Programme for Centres of Excellence in R&D (MINECO, Grant SEV2016-0686). R.R.T. acknowledges funding from the Natural Sciences and Engineering Research Council of Canada (NSERC, grant no. RGPIN-2017-05052) and the Canada Foundation for Innovation (CFI

Stable and Solution-Processable Cumulenic sp-Carbon Wires: A New Paradigm for Organic Electronics

[EN] Solution-processed, large-area, and flexible electronics largely relies on the excellent electronic properties of sp(2)-hybridized carbon molecules, either in the form of pi-conjugated small molecules and polymers or graphene and carbon nanotubes. Carbon with sp-hybridization, the foundation of the elusive allotrope carbyne, offers vast opportunities for functionalized molecules in the form of linear carbon atomic wires (CAWs), with intriguing and even superior predicted electronic properties. While CAWs represent a vibrant field of research, to date, they have only been applied sparingly to molecular devices. The recent observation of the field-effect in microcrystalline cumulenes suggests their potential applications in solution-processed thin-film transistors but concerns surrounding the stability and electronic performance have precluded developments in this direction. In the present study, ideal field-effect characteristics are demonstrated for solution-processed thin films of tetraphenyl[3]cumulene, the shortest semiconducting CAW. Films are deposited through a scalable, large-area, meniscus-coating technique, providing transistors with hole mobilities in excess of 0.1 cm(2 )V(-1 )s(-1), as well as promising operational stability under dark conditions. These results offer a solid foundation for the exploitation of a vast class of molecular semiconductors for organic electronics based on sp-hybridized carbon systems and create a previously unexplored paradigm.E.G.F. acknowledges the support through the EU Horizon 2020 research and innovation program, H2020-FETOPEN-01-2018-2020 (FET-Open Challenging Current Thinking), "LION-HEARTED", grant agreement no. 828984. C.S.C. acknowledges funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program ERC-Consolidator Grant (ERC CoG 2016 EspLORE grant agreement no. 724610, website: ). R.R.T. acknowledges funding from the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canada Foundation for Innovation (CFI). This work was partially supported by the European Union's H2020-EU.4.b. - Twinning of research institutions "GREENELIT", grant agreement number 951747. GIWAXS experiments were performed at BL11 NCD-SWEET beamline at ALBA Synchrotron (Spain) with the collaboration of ALBA staff. This work was in part carried out at Polifab, the micro- and nanotechnology centre of the Politecnico di Milano. Open access funding provided by Istituto Italiano di Tecnologia within the CRUI-CARE Agreement

Stable and Solution-Processable Cumulenic sp-Carbon Wires: A New Paradigm for Organic Electronics

open12siAcknowledgements. E.G.F. acknowledges the support through the EU Horizon 2020 research and innovation program, H2020-FETOPEN-01-2018-2020 (FET-Open Challenging Current Thinking), “LION-HEARTED”, grant agreement no. 828984. C.S.C. acknowledges funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program ERC-Consolidator Grant (ERC CoG 2016 EspLORE grant agreement no. 724610, website: www.esplore.polimi.it). R.R.T. acknowledges funding from the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canada Foundation for Innovation (CFI). This work was partially supported by the European Union's H2020-EU.4.b. – Twinning of research institutions “GREENELIT”, grant agreement number 951747. GIWAXS experiments were performed at BL11 NCD-SWEET beamline at ALBA Synchrotron (Spain) with the collaboration of ALBA staff. This work was in part carried out at Polifab, the micro- and nanotechnology centre of the Politecnico di Milano. Open access funding provided by Istituto Italiano di Tecnologia within the CRUI-CARE Agreement.Solution-processed, large-area, and flexible electronics largely relies on the excellent electronic properties of sp2-hybridized carbon molecules, either in the form of π-conjugated small molecules and polymers or graphene and carbon nanotubes. Carbon with sp-hybridization, the foundation of the elusive allotrope carbyne, offers vast opportunities for functionalized molecules in the form of linear carbon atomic wires (CAWs), with intriguing and even superior predicted electronic properties. While CAWs represent a vibrant field of research, to date, they have only been applied sparingly to molecular devices. The recent observation of the field-effect in microcrystalline cumulenes suggests their potential applications in solution-processed thin-film transistors but concerns surrounding the stability and electronic performance have precluded developments in this direction. In the present study, ideal field-effect characteristics are demonstrated for solution-processed thin films of tetraphenyl[3]cumulene, the shortest semiconducting CAW. Films are deposited through a scalable, large-area, meniscus-coating technique, providing transistors with hole mobilities in excess of 0.1 cm2V−1s−1, as well as promising operational stability under dark conditions. These results offer a solid foundation for the exploitation of a vast class of molecular semiconductors for organic electronics based on sp-hybridized carbon systems and create a previously unexplored paradigm.openPecorario S.; Scaccabarozzi A.D.; Fazzi D.; Gutierrez-Fernandez E.; Vurro V.; Maserati L.; Jiang M.; Losi T.; Sun B.; Tykwinski R.R.; Casari C.S.; Caironi M.Pecorario S.; Scaccabarozzi A.D.; Fazzi D.; Gutierrez-Fernandez E.; Vurro V.; Maserati L.; Jiang M.; Losi T.; Sun B.; Tykwinski R.R.; Casari C.S.; Caironi M