Synthesis of indano[60]fullerene thioketone and its application in organic solar cells.

Evaporable indano[60]fullerene ketone (FIDO) was converted to indano[60]fullerene thioketone (FIDS) in high yield by using Lawesson's reagent. Three compounds with different substituents in para position were successfully converted to the corresponding thioketones, showing that the reaction tolerates compounds with electron-donating and electron-withdrawing substituents. Computational studies with density functional theory revealed the unique vibrations of the thioketone group in FIDS. The molecular structure of FIDS was confirmed by single-crystal X-ray analysis. Bulk heterojunction organic solar cells using three evaporable fullerene derivatives (FIDO, FIDS, C60) as electron-acceptors were compared, and the open-circuit voltage with FIDS was 0.16 V higher than that with C60.

Manipulating the functionality and structures of π-conjugated polymers utilizing intramolecular noncovalent interactions towards efficient organic photovoltaics.

Careful control of electronic properties, structural order, and solubility of π-conjugated polymers is central to the improvement of organic photovoltaic (OPV) performance. In this work, we designed and synthesized a series of naphthobisthiadiazole-quaterthiophene copolymers by systematically replacing the alkyl groups with ester groups and changing the position of the fluorine groups in the quaterthiophene moiety. These alterations lowered the HOMO and LUMO energy levels and systematically varied the combination of intramolecular noncovalent interactions such as O⋯S and F⋯S interactions in the backbone. More importantly, although the introduction of such noncovalent interactions often lowers the solubility owing to the interlocking of backbone linkages, we found that careful design of the noncovalent interactions afforded polymers with relatively high solubility and high crystallinity at the same time. As a result, the power conversion efficiency of OPV cells that used fullerene (PC61BM) and nonfullerene (Y12) as the acceptor was improved. Our work offers important information for the development of high-performance π-conjugated polymers for OPVs.

Simple π-Conjugated Polymers Based on Bithiazole for Nonfullerene Organic Photovoltaics.

Thiazole, as a family of five-membered heteroaromatic rings, is an interesting building unit that can play a role in coplanarizing the backbone as well as deepening the HOMO energy level, which is beneficial for the design of π-conjugated polymers for the photoactive materials in organic photovoltaics (OPVs). Here, we designed and synthesized π-conjugated polymers with simple chemical structures, which consist of 2,2'-bithiazole or 5,5'-bithiazole and alkylthiophenes as the polymer backbone. In fact, the polymers can be easily synthesized in much fewer steps compared to the typical high-performance polymers based on fused heteroaromatic rings. Interestingly, PTN5 exhibited a markedly higher ordered structure than PTN2. This was likely ascribed to the more coplanar and rigid backbone of PTN5 than that of PTN2 originating in the effectively arranged S···N interaction. As a result, the nonfullerene photovoltaic cell based on PTN5 showed a PCE of 12.2%, which was much higher than the cell based on PTN2 (4.3%) and was high for the polymers consisting of only nonfused rings. These results demonstrate that thiazole-based polymers are promising photoactive materials for OPVs and emphasize the importance of careful molecular design utilizing noncovalent interactions.

Dependence of Exciton Binding Energy on Bandgap of Organic Semiconductors.

Strongly bound excitons crucially affect the operation of organic optoelectronic devices. Nevertheless, precise experimental data on the exciton binding energy of organic semiconductors are lacking. In this study, we determine the exciton binding energy as the difference between the optical and transport bandgaps with a precision of 0.1 eV. In particular, electron affinities with a precision higher than 0.05 eV determined by low-energy inverse photoelectron spectroscopy allow us to determine the transport gap and the exciton binding energies with such high precision. Through a systematic comparison of a wide range of organic semiconductors, including 42 organic solar cell materials (15 nonfullerene acceptors, 4 fullerene acceptors, 13 low-bandgap polymers, 7 organic light-emitting diode materials, and 3 crystalline materials), we found that the exciton binding energy is one-quarter of the transport gap regardless of the materials. We interpret this unexpected relation from a hydrogen atom-like model, i.e., the quantized energy levels in a Coulomb potential between the positive and the negative charges.

Halogen-Free π $\upi$ -Conjugated Polymers Based on Thienobenzobisthiazole for Efficient Nonfullerene Organic Solar Cells: Rational Design for Achieving High Backbone Order and High Solubility.

In π $\upi$ -conjugated polymers, a highly ordered backbone structure and solubility are always in a trade-off relationship that must be overcome to realize highly efficient and solution-processable organic photovoltaics (OPVs). Here, it is shown that a π $\upi$ -conjugated polymer based on a novel thiazole-fused ring, thieno[2',3':5,6]benzo[1,2-d:4,3-d']bisthiazole (TBTz) achieves both high backbone order and high solubility due to the structural feature of TBTz such as the noncovalent interlocking of the thiazole moiety, the rigid and bent-shaped structure, and the fused alkylthiophene ring. Furthermore, based on the electron-deficient nature of these thiazole-fused rings, the polymer exhibits deep HOMO energy levels, which lead to high open-circuit voltages (VOC s) in OPV cells, even without halogen substituents that are commonly introduced into high-performance polymers. As a result, when the polymer is combined with a typical nonfullerene acceptor Y6, power conversion efficiencies of reaching 16% and VOC s of more than 0.84 V are observed, both of which are among the top values reported so far for "halogen-free" polymers. This study will serve as an important reference for designing π $\upi$ -conjugated polymers to achieve highly efficient and solution-processable OPVs.

Naphthobisthiadiazole-Based π-Conjugated Polymers for Nonfullerene Solar Cells: Suppressing Intermolecular Interaction Improves Photovoltaic Performance.

Naphthobisthiadiazole has been known as a promising building unit of π-conjugated polymers for organic photovoltaics (OPVs). Here, we synthesized new NTz-based polymers that were combined with a benzodithiophene (BDT) unit having alkylthienyl substituents in the polymer backbone, named PNTzBDT, and PNTzBDT-F and PNTzBDT-Cl with fluorine and chlorine groups in the substituents, respectively. The polymers had significantly improved solubility than the previously reported NTz-based polymer (PNTz4T), most likely due to the torsion of the alkylthienyl substituents with respect to the BDT moiety, which suppresses the intermolecular interaction between the backbones. Despite the lower intermolecular interaction and thereby lower crystallinity, these polymers, in particular PNTzBDT and PNTzBDT-F, exhibited higher photovoltaic performances, with power conversion efficiencies as high as 13.3%, than PNTz4T in the cells that used Y6 as the acceptor material. The improved performance was ascribed to the enhanced miscibility of the polymers with the nonfullerene acceptor due to the increased solubility, which in addition led to the better charge generation and reduced charge recombination. These results indicate that NTz-based π-conjugated polymers have high potential for nonfullerene-based OPVs.

Pronounced Backbone Coplanarization by π-Extension in a Sterically Hindered Conjugated Polymer System Leads to Higher Photovoltaic Performance in Non-Fullerene Solar Cells.

Achieving both the backbone order and solubility of π-conjugated polymers, which are often in a trade-off relationship, is imperative for maximizing the performance of organic solar cells. Here, we studied three different π-conjugated polymers based on thiazolothiazole (PSTz1 and POTz1) and benzobisthiazole (PNBTz1) that were combined with a benzodithiophene unit in the backbone, where PNBTz1 was newly synthesized. Because of the steric hindrance between the side chains located on neighboring heteroaromatic rings, POTz1 had a much less coplanar backbone than PSTz1 in which such a steric hindrance is absent. However, POTz1 showed higher photovoltaic performance in solar cells that used Y6 as the acceptor material. This was likely due to the significantly higher solubility of POTz1 than PSTz1, resulting in a better morphology. Interestingly, PNBTz1 was found to have markedly higher backbone coplanarity than POTz1, despite having similar steric hindrance between the side chains, most likely owing to the more extended π-electron system, whereas PNBTz1 had good solubility comparable to POTz1. As a result, PNBTz1 exhibited higher photovoltaic performance than POTz1 in the Y6-based cells: specifically, the fill factor was significantly enhanced. Our results indicate that the backbone order and solubility can be achieved by the careful molecular design, which indeed leads to higher photovoltaic performance.

Contrasting Effect of Side-Chain Placement on Photovoltaic Performance of Binary and Ternary Blend Organic Solar Cells in Benzodithiophene-Thiazolothiazole Polymers.

π-Conjugated polymers are important materials for organic photovoltaics. While search for new backbone systems is central to the development of π-conjugated polymers, side-chain engineering is also imperative. Here, two benzodithiophene-thiazolothiazole copolymers, PSTz1 and POTz1, were synthesized, for which the side-chain placement was different. Due to less steric hindrance between the side chains, PSTz1 had a more coplanar backbone than POTz1. This led to significant differences in trend of the performance for the binary and ternary blend cells that used a fullerene (PC71 BM) and/or non-fullerene (ITIC) as the acceptor materials. Whereas PSTz1 showed higher photovoltaic performance in the PC71 BM-based cell, POTz1 showed higher performance in the ITIC-based cell. Furthermore, in the ternary blend cell, whereas increase in the PC71 BM content improved the photovoltaic performance for the PSTz1 system, it was detrimental to the performance for the POTz1 system. These results could be a good guideline for maximizing the performance of organic photovoltaics.

Molecular Understanding of How the Interfacial Structure Impacts the Open-Circuit Voltage of Highly Crystalline Polymer Solar Cells.

Herein, we study the origin of differences in open-circuit voltage (VOC) for polymer:fullerene solar cells employing highly crystalline conjugated polymers (PTzBT) based on the same thiophene-thiazolothiazole backbone with different side chains. By analyzing the temperature dependence of VOC and cyclic voltammogram, we find that the difference in VOC originates in the different cascaded energy structures for the highest occupied molecular orbital (HOMO) levels in the interfacial mixed phase. Furthermore, we find that this is due to the stabilization of HOMO caused by the different branching of side chains on the basis of density functional theory calculation. Finally, we discuss the molecular design strategy based on side-chain engineering for ideal interfacial cascaded energy structures leading to higher VOC and photocurrent simultaneously.

Self-powered ultraflexible photonic skin for continuous bio-signal detection via air-operation-stable polymer light-emitting diodes.

Ultraflexible optical devices have been used extensively in next-generation wearable electronics owing to their excellent conformability to human skins. Long-term health monitoring also requires the integration of ultraflexible optical devices with an energy-harvesting power source; to make devices self-powered. However, system-level integration of ultraflexible optical sensors with power sources is challenging because of insufficient air operational stability of ultraflexible polymer light-emitting diodes. Here we develop an ultraflexible self-powered organic optical system for photoplethysmogram monitoring by combining air-operation-stable polymer light-emitting diodes, organic solar cells, and organic photodetectors. Adopting an inverted structure and a doped polyethylenimine ethoxylated layer, ultraflexible polymer light-emitting diodes retain 70% of the initial luminance even after 11.3 h of operation under air. Also, integrated optical sensors exhibit a high linearity with the light intensity exponent of 0.98 by polymer light-emitting diode. Such self-powered, ultraflexible photoplethysmogram sensors perform monitoring of blood pulse signals as 77 beats per minute.

Visible light-driven Giese reaction with alkyl tosylates catalysed by nucleophilic cobalt.

The scope of the Giese reaction is expanded using readily available alkyl tosylates as substrates and nucleophilic cobalt(i) catalysts under visible-light irradiation. The reaction proceeds preferentially with less bulky primary alkyl tosylates. This unique reactivity enables the regio-selective Giese reaction of polyol derivatives.

Reductive amidation of alkyl tosylates with isocyanates by a Ni/Co-dual catalytic system.

Reductive amidation of alkyl tosylates with isocyanates using the Ni/Co-dual catalytic system is disclosed. The method proceeds efficiently under mild conditions, giving rise to the corresponding alkyl amides. Notably, the protocol can discriminate the steric environment of two alkyl tosylate moieties, enabling regioselective mono-amidation at the less-bulky site.

[A case of transverse colon cancer with idiopathic mesenteric phlebosclerosis].

A 74-year-old male was diagnosed with transverse colon carcinoma with idiopathic mesenteric phlebosclerosis (IMP). Extended right hemicolectomy with regional lymph node dissection was performed. It has been reported that IMP develops after taking Chinese herbs containing SANSIS for a long time. In this case, the patient had taken such an herb for more than 3 years. In Japan, total 6 cases have been reported on a tumor with IMP, including this case. Immunohistological examination showed that the IMP findings were particularly strong around the tumor. Thus, this case suggests that there is a link between the tumor and IMP.

Dithiazolylthienothiophene Bisimide: A Novel Electron-Deficient Building Unit for N-Type Semiconducting Polymers.

N-type (electron-transporting) semiconducting polymers are essential materials for the development of truly plastic electronic devices. Here, we synthesized for the first time dithiazolylthienothiophene bisimide (TzBI), as a new family for imide-based electron-deficient π-conjugated systems, and semiconducting polymers by incorporating TzBI into the π-conjugated backbone as the building unit. The TzBI-based polymers are found to have deep frontier molecular orbital energy levels and wide optical bandgaps compared to the dithienylthienothiophene bisimide (TBI) counterpart. It is also found that TzBI can promote the π-π intermolecular interactions of the polymer backbones relative to TBI most probably because the thiazole ring, which replaced the thiophene ring, at the end of the framework gives a more coplanar backbone. In fact, TzBI-based polymers function as the n-type semiconducting material in both organic field-effect transistor (OFET) and organic photovoltaic (OPV) devices. Notably, one of the TzBI-based polymers provides a power conversion efficiency of 3.3% in the all-polymer OPV device, which could be high for a low-molecular-weight polymer (<10 kDa). Interestingly, while many of the n-type semiconducting polymers utilized in OPVs have narrow bandgaps, the TzBI-based polymers have wide bandgaps. This is highly beneficial for complementing the visible to near-IR light absorption range when blended with p-type narrow bandgap polymers that have been widely developed in the last decade. The results demonstrate great promise and possibility of TzBI as the building unit for n-type semiconducting polymers.

Copper-catalyzed arylstannylation of arynes in a sequence.

Copper-catalyzed arylstannylation of arynes has been developed. This transformation enables variously substituted ortho-stannylbiaryls and teraryls to be constructed straightforwardly. An electron-deficient tin center is the key, and thus the single or dual insertion of arynes into arylstannanes is precisely controllable by simply changing the equivalence of aryne precursors.

An anthranilamide-substituted borane [H-B(aam)]: its stability and application to iridium-catalyzed stereoselective hydroboration of alkynes.

A new anthranilamide-substituted borane [H-B(aam)] was synthesized and found to serve as a stable, easy-to-handle substitute for H-B(pin). It was applied to the direct synthesis of diverse linear (E)-alkenyl-B(aam)s via regio- and stereoselective hydroboration of terminal alkynes under iridium catalysis. A boryliridium hydride complex arising from the oxidative addition of H-B(aam) to the Ir catalyst was isolated and characterized via NMR studies.

Ni/Co-Catalyzed Homo-Coupling of Alkyl Tosylates.

A direct reductive homo-coupling of alkyl tosylates has been developed by employing a combination of nickel and nucleophilic cobalt catalysts. A single-electron-transfer-type oxidative addition is a pivotal process in the well-established nickel-catalyzed coupling of alkyl halides. However, the method cannot be applied to the homo-coupling of ubiquitous alkyl tosylates due to the high-lying σ*(C-O) orbital of the tosylates. This paper describes a Ni/Co-catalyzed protocol for the activation of alkyl tosylates on the construction of alkyl dimers under mild conditions.

High Operation Stability of Ultraflexible Organic Solar Cells with Ultraviolet-Filtering Substrates.

Ultralightweight and flexible power sources are essential for driving textile or wearable electronic devices and soft robots because they do not induce discomfort or limit movement when they are attached to human skin, textiles, or soft actuators. Organic solar cells (OSCs) are good candidates for developing such power sources because they have the advantages of being lightweight and flexible. However, achieving operational stability and ultrathin shape simultaneously remains difficult because the ultrathin substrate cannot prevent the penetration of ultraviolet (UV) light, which is major a cause for the degradation of OSCs. Here, ultrathin OSCs that show great operational stability and high performance are reported. The 1.3 µm thick transparent polyimide utilized as a substrate can block light of 350 nm wavelength in the UV range by 90%. The ultrathin OSCs with the transparent polyimide substrate produce a power conversion efficiency (PCE) of 9.0% and realize both photostability and operational stability. The PCE was maintained at 90% after 3 h in a maximum power point tracking test, indicating much better operational stability than the reference rigid OSCs.

Anthranilamide (aam)-substituted arylboranes in direct carbon-carbon bond-forming reactions.

Anthranilamide (aam)-substituted arylboranes, which were reported to serve as masked boranes in the Suzuki-Miyaura coupling, have been found to be directly cross-coupled just by use of an aqueous medium. The excellent stability of 2-pyridyl-B(aam) toward protodeborylation allowed their smooth cross-coupling.

Scalable Ultrasonic Spray-Processing Technique for Manufacturing Large-Area CH3NH3PbI3 Perovskite Solar Cells.

Organic-inorganic hybrid perovskite solar cells are on the brink of a breakthrough in photovoltaic technology. Scale-up and large-area processing have become the focal points that must be resolved before commercialization. In this study, the scalable ultrasonic spray deposition method for high-throughput coating of the perovskite photoactive layer with a large active area of up to 3 cm2 is implemented by precisely controlling the concentration of the precursor solution and spray passes. CH3NH3PbI3 films with large crystallites and a suitable thickness of ∼350 nm are facilely developed through one-step direct ultrasonic spraying. Less hysteresis and highly reproducible power conversion efficiencies (PCEs) of up to 12.30% (11.43 ± 0.43% on average for 20 devices) are achieved by an optimized single-junction device with an active area of 1 cm2, along with good ambient stability. The device retained ∼80 and ∼65% of the initial PCE after 60 and 105 days in ambient, respectively. The ultrasonic spray-coated perovskite solar cells can be further scaled to larger areas of 2 and 3 cm2 and exhibit PCEs of 10.18 and 7.01%, respectively. The reliable scale-up process for manufacturing the atmospheric wet-coated perovskite film is available in cost-effective and easily operated bench-top variants to bridge the interconnection between applied research and industry.