Synthesis of Organic Semiconductors Based on Fused Heteroacenes for Optoelectronic Applications

Energy EngineeringOrganic semiconductors have attracted much interest for future electronic devices such as organic light emitting diodes (OLEDs), organic field-effect transistors (OFETs), organic photovoltaics (OPVs), dye-sensitized solar cells (DSSCs) and so on due to many potential merits like light weight, low cost, flexibilty and solution processablity. Despite considerable studies for material science and device physics related to organic semiconductors, a better understanding of the efficient molecular design and systemical optimization is highly required for further development of organic electronics. So far, organic semiconductors based on rigid and π-conjugated molecular backbones that synthesized by powerful cross-coupling reaction methodologies have exhibited promising device performance. Among those, especially fused acenes or hetercyclic architecture has many advantages such as strong intermolecular interaction, increased coplanarity, reduced bandgap and good charge carrier transport. However, restricted synthetic methods hinder various modification of electronic properties of organic semiconductors with fused ring systems. In this work, synthesis of organic semiconductors based on such fused or cyclized heteroacenes and their optoelectronic applications are presented. Firstly, a thiophene-fused ladderized heteroacene dye is designed and synthesized via efficienct synthetic pathways. The fused material is used as a metal-free organic photosensitizer for DSSCs and the light harvesting property is characterized. Secondly, a nitrogen-fused cycle, carbazole-based semicondcutor PCDTBT, which is one of promising photoactive p-type polymer in organic bulk-heterojuction solar cells, is modified via incorporation of different electron-deficient units such as bisbenzothiadiazole, naphthothiadiazole and fluorinated benzothiadiazoles for systemical studies of structure-property relationship. The synthetic procedures and characterization of optical and electronic properties in OPVs are presented for each resulting PCDTBT derivative. Finally, a highly π-extended heteroacene, dithieno[2,3-d;2′,3′-d′]benzo[1,2-b;4,5-b′]dithiophene (DTBDT), with α-positions availability is prepared via the synthesis of a key intermediate. The homopolymer and copolymers are synthesized for the first time and their properties are fully characterized. All polymers based on DTBDT are applied as p-type materials for OFETs.ope

A synthetic approach to a fullerene-rich dendron and its linear polymer via ring-opening metathesis polymerization

Through the esterification of an acyl chloride functionalized fullerene precursor with dendritic alcohol, a fullerene-rich dendron containing a norbornene unit at the focal point is prepared for ring-opening metathesis polymerization to obtain its linear polymer with a unimodal and narrow molar mass distribution (PDI = 1.08) by a progressive addition of catalysts.close181

Evaluation of persistent-mode operation in a superconducting MgB2 coil in solid nitrogen

We report the fabrication of a magnesium diboride (MgB2) coil and evaluate its persistent-mode operation in a system cooled by a cryocooler with solid nitrogen (SN2) as a cooling medium. The main purpose of SN2 was to increase enthalpy of the cold mass. For this work, an in situ processed carbon-doped MgB2 wire was used. The coil was wound on a stainless steel former in a single layer (22 turns), with an inner diameter of 109 mm and height of 20 mm without any insulation. The two ends of the coil were then joined to make a persistent-current switch to obtain the persistent-current mode. After a heat treatment, the whole coil was installed in the SN2 chamber. During operation, the resultant total circuit resistance was estimated to be \u3c7.4x10−14 Ω at 19.5 K±1.5 K, which meets the technical requirement for magnetic resonance imaging application

Subclassification of advanced-stage hepatocellular carcinoma with macrovascular invasion: combined transarterial chemoembolization and radiotherapy as an alternative first-line treatment

Background/Aim The Barcelona Clinic Liver Cancer (BCLC) guidelines recommend systemic therapy as the only first-line treatment for patients with BCLC stage C hepatocellular carcinoma (HCC) despite its heterogeneity of disease extent. We aimed to identify patients who might benefit from combined transarterial chemoembolization (TACE) and radiation therapy (RT) by subclassifying BCLC stage C. Methods A total of 1,419 treatment-naïve BCLC stage C patients with macrovascular invasion (MVI) who were treated with combined TACE and RT (n=1,115) or systemic treatment (n=304) were analyzed. The primary outcome was overall survival (OS). Factors associated with OS were identified and assigned points by the Cox model. The patients were subclassified into three groups based on these points. Results The mean age was 55.4 years, and 87.8% were male. The median OS was 8.3 months. Multivariate analysis revealed a significant association of Child-Pugh B, infiltrative-type tumor or tumor size ≥10 cm, main or bilateral portal vein invasion, and extrahepatic metastasis with poor OS. The sub-classification was categorized into low (point ≤1), intermediate (point=2), and high (point ≥3) risks based on the sum of points (range, 0–4). The OS in the low, intermediate, and high-risk groups was 22.6, 8.2, and 3.8 months, respectively. In the low and intermediate-risk groups, patients treated with combined TACE and RT exhibited significantly longer OS (24.2 and 9.5 months, respectively) than those who received systemic treatment (6.4 and 5.1 months, respectively; P<0.0001). Conclusions Combined TACE and RT may be considered as a first-line treatment option for HCC patients with MVI when classified into low- and intermediate-risk groups

Organic-Inorganic Nanostructure Architecture via Directly Capping Fullerenes onto Quantum Dots

A new form of fullerene-capped CdSe nanoparticles (PCBA-capped CdSe NPs), using carboxylate ligands with [60] fullerene capping groups that provides an effective synthetic methodology to attach fullerenes noncovalently to CdSe, is presented for usage in nanotechnology and photoelectric fields. Interestingly, either the internal charge transfer or the energy transfer in the hybrid material contributes to photoluminescence (PL) quenching of the CdSe moieties.open2

Synthesis and photophysical properties of five-membered ring pi-conjugated materials based on bisthiazol-2-yl-amine and their metal complexation studies

Poly(5,5'-(2-hexyldecyl)-bisthiazol-2-yl-amine) (PBTA) is prepared by nickel(0) mediated Yamamoto-type coupling. The photoluminescence (PL) spectrum of PBTA in THF solution displays pure blue emission with a peak centered at 444 nm without any shoulder peaks and the HOMO and LUMO values for PBTA are estimated to be 5.11 and 2.90 eV, respectively. In addition, we have synthesized a novel bisthiazol-2-yl-amine (BTA)-cored donor acceptor (D A) chromophore system, namely 5-(4-(diphenylamino)phenyl)-N-(5-(4-(diphenylamino)phenyl)thiazol-2-yl)-N-octylthiazol-2-amine (2-TPA-BTA) in which the electron-donating (D) moiety is triphenylamine group and the electron-withdrawing (A) unit is thiazole group. Furthermore, in this report, we present the complexation studies of both the BTA and 2-TPA-BTA chromophores with Cu(II) and Pd(II), respectively. The crystal structures are established by single-crystal X-ray diffraction analysis. These studies not only provide the general photophysical principles of the materials based on BTA moiety but also encourage progress toward realizing the full potential of its hybrid metal organic frameworks.close

Organic&#8211;Inorganic Nanostructure Architecture via Directly Capping Fullerenes onto Quantum Dots

Abstract A new form of fullerene-capped CdSe nanoparticles (PCBA-capped CdSe NPs), using carboxylate ligands with [60]fullerene capping groups that provides an effective synthetic methodology to attach fullerenes noncovalently to CdSe, is presented for usage in nanotechnology and photoelectric fields. Interestingly, either the internal charge transfer or the energy transfer in the hybrid material contributes to photoluminescence (PL) quenching of the CdSe moieties.</p

A simultaneous achievement of high performance and extended thermal stability of bulk-heterojunction polymer solar cells using a polythiophene-fullerene block copolymer

We report substantial improvements in efficiency and thermal stability of the poly(3-hexylthiophene):[6.6]-phenyl-C-61-butyric acid methyl ester (PCBM) (P3HT:PCBM) bulk heterojunction (BHJ) system by adding a diblock copolymer P3HT-b-P(St(89)BAz(11))-C-60 (P3HT=poly (3-hexylthiophene), St=styrene, BAz=benzyl aside) as a compatibilizer. Small amounts of the diblock copolymer alter the interfacial morphology between the P3HT and PCBM components, resulting in a noticeable difference in phase segregation of the BHJ films, as evident in atomic force microscopy images. The best performance is observed in the P3HT:PCBM cell with 10% P3HT-b-P(St(89)BAz(11))-C-60, which exhibits substantially improved power conversion efficiency and thermal stability compared to the P3HT:PCBM control device.close1