Electron-rich Building Block Research Articles

EDOT-based conjugated polymers accessed via C-H direct arylation for efficient photocatalytic hydrogen production.

3,4-Ethylene dioxythiophene (EDOT), as a monomer of commercial conductive poly(3,4-ethylene dioxythiophene) (PEDOT), has been facilely incorporated into a series of new π-conjugated polymer-based photocatalysts, i.e., BSO2–EDOT, DBT–EDOT, Py–EDOT and DFB–EDOT, through atom-economic C–H direct arylation polymerization (DArP). The photocatalytic hydrogen production (PHP) test shows that donor–acceptor (D–A)-type BSO2–EDOT renders the highest hydrogen evolution rate (HER) among the linear conjugated polymers (CPs) ever reported. A HER up to 0.95 mmol h−1/6 mg under visible light irradiation and an unprecedented apparent quantum yield of 13.6% at 550 nm are successfully achieved. Note that the photocatalytic activities of the C–H/C–Br coupling-derived EDOT-based CPs are superior to those of their counterparts derived from the classical C–Sn/C–Br Stille coupling, demonstrating that EDOT is a promising electron-rich building block which can be facilely integrated into CP-based photocatalysts. Systematic studies reveal that the enhanced water wettability by the integration of polar BSO2 with hydrophilic EDOT, the increased electron-donating ability by O–C p–π conjugation, the improved electron transfer by D–A architecture, broad light harvesting, and the nano-sized colloidal character in a H2O/NMP mixed solvent rendered BSO2–EDOT as one of the best CP photocatalysts toward PHP.

Wide Band-gap Two-dimension Conjugated Polymer Donors with Different Amounts of Chlorine Substitution on Alkoxyphenyl Conjugated Side Chains for Non-fullerene Polymer Solar Cells

In this study, wide bandgap (WBG) two-dimensional (2D) copolymer donors (DZ1, DZ2, and DZ3) based on benzodithiophene (BDT) on alkoxyphenyl conjugated side chains without and with different amounts of chlorine atoms and difluorobenzotriazole (FBTZ) are designed and synthesized successfully for efficient non-fullerene polymer solar cells (PSCs). Three polymer donors DZ1, DZ2, and DZ3 display similar absorption spectra at 300–700 nm range with optional band-gap (Egopt) of 1.84, 1.92, and 1.97 eV, respectively. Compared with reported DZ1 without chlorine substitution, it is found that introducing chlorine atoms into the meta-position of the alkoxyphenyl group affords polymer possessing a deeper the highest occupied molecular orbital (HOMO) energy level, which can increase open circuit voltage (VOC) of PSCs, as well as improve hole mobility. Non-fullerene bulk heterojunction PSCs based on DZ2:MeIC demonstrate a relatively high power conversion efficiency (PCE) of 10.22% with a VOC of 0.88 V, a short-circuit current density (JSC) of 17.62 mA/cm2, and a fill factor (FF) of 68%, compared with PSCs based on DZ1:MeIC (a PCE of 8.26%) and DZ3:MeIC (a PCE of 6.28%). The results imply that adjusting chlorine atom amount on alkoxyphenyl side chains based on BDT polymer donors is a promising approach of synthesizing electron-rich building block for high performance of PSCs.

Enhancement of the thermoelectric performance of DPP based polymers by introducing one 3,4-ethylenedioxythiophene electron-rich building block

The incorporation of one 3,4-ethylenedioxythiophene (EDOT) building block into a diketopyrrolopyrrole (DPP) based D–A conjugated polymer could facilitate the p-doping of a D–A conjugated polymer and improve thermoelectric performance.

Diverse Isoquinoline Scaffolds by Ugi/Pomeranz-Fritsch and Ugi/Schlittler-Müller Reactions.

The Pomeranz–Fritsch reaction and its Schlittler–Müller modification were successfully applied in the Ugi postcyclization strategy by using orthogonally protected aminoacetaldehyde diethyl acetal and complementary electron rich building blocks. Several scaffolds, including isoquinolines, carboline, alkaloid-like tetrazole-fused tetracyclic compounds, and benzo[d]azepinone scaffolds, were synthesized in generally moderate to good yield. All our syntheses provide a short MCR-based sequence to novel or otherwise difficult to access scaffolds. Hence, we foresee multiple applications of these synthesis technologies.

All-polymer solar cells based on photostable bis(perylene diimide) acceptor polymers

Fullerene-free organic photovoltaics have recently reached impressive power conversion efficiencies above 14% for single junctions, increasing their competitiveness with respect to alternative thin-film technologies. In most record devices, electron-donating conjugated polymers are combined with novel generation small molecule acceptors. All-polymer organic solar cells, on the other hand, still lag behind in efficiency, although they have specific advantages in terms of ink formulation and long-term operational stability. Another point of attention is the synthetic complexity of the active layer materials, notably on the side of the new acceptor molecules. Therefore, the present study focuses on the implementation of the stable and cost-effective perylene diimide structure as the key component of high-performance electron-accepting polymers. The synthesis, structural and optoelectronic characterization of four push-pull type copolymers containing the electron-deficient bis(perylene diimide) (bis-PDI) unit is reported, as well as the photovoltaic analysis of these acceptor materials in combination with a well-known donor polymer (PTB7-Th). The acceptor polymers differ in the electron-rich part of the alternating push-pull structure and their solar cell power conversion efficiencies range from 3.2 to 4.7%. The maximum efficiency - the best performance achieved with a bis-PDI polymer so far - is obtained for the structurally most simple polymer, containing merely thiophene as the electron-rich building block. Controlled degradation under blue light in air is monitored by the bleaching of the relevant UV–Vis absorption bands, demonstrating high stability for the bis-PDI-thiophene containing polymers as compared to some prototype small molecule acceptors (FBR and ITIC).

Metallated conjugation in small-sized-molecular donors for solution-processed organic solar cells

Four metallated conjugated oligothiophenes, S-1, S-2, S-3 and S-4, with platinum(II) aryleneethynylenes as the electron-rich building block were synthesized to investigate their physicochemical and photovoltaic properties. These small molecules possess fairly low-lying HOMO energy levels which match with the LUMO energy level of the electron acceptor PC70BM ([6,6]-phenyl-C71-butyric acid methyl ester). Using the simple process of spin-coating solution fabrication technique, S-1:PC70BM (1:4, w/w) based organic solar cells exhibiting a high V oc of 0.913 V, with a PCE value of 0.88% were developed. In contrast, the OSC device based on S-2:PC70BM (3:7, w/w) displayed a higher PCE of 1.59% with a higher J sc value of 5.89 mA cm−2. The device based on S-4:PC70BM (1:4, w/w) exhibited a PCE value of 1.56%, with a V oc of 0.917 V.

Dithieno[2,3-d:2′,3′-d′]naphtho[1,2-b:3,4-b′]dithiophene – a novel electron-rich building block for low band gap conjugated polymers

A feasible synthesis of 10,11-di(3,7-dimethyloctyloxy)dithieno[2,3-d:2′,3′-d′]naphtho[1,2-b:3,4-b′]dithiophene (NDT) was presented, and a novel low band gap (LBG) NDT-based polymer was prepared and characterized. The preliminary results indicate that NDT can be used as a novel electron-rich building block in the development of LBG conjugated polymers.

Synthesis of 6H-benzo[c]chromene as a new electron-rich building block of conjugated alternating copolymers and its application to polymer solar cells

PBCDTBTandPBCDPP2Tare synthesized by introducing an oxygen atom in the fluorene unit inPFDTBTandPFDPP2T, respectively.PBCDTBT- andPBCDPP2T-based devices exhibit higherJSCs thanPFDTBTandPFDPP2T-based devices, respectively.

Synthesis of 5H-Dithieno[3,2-b:2′,3′-d]pyran as an Electron-Rich Building Block for Donor–Acceptor Type Low-Bandgap Polymers

We describe the detailed synthesis and characterization of an electron-rich building block, dithienopyran (DTP), and its application as a donor unit in low-bandgap conjugated polymers. The electron-donating property of the DTP unit was found to be the strongest among the most frequently used donor units such as benzodithiophene (BDT) or cyclopentadithiophene (CPDT) units. When the DTP unit was polymerized with the strongly electron-deficient difluorobenzothiadiazole (DFBT) unit, a regiorandom polymer (PDTP–DFBT, bandgap = 1.38 eV) was obtained. For comparison with the DTP unit, polymers containing alternating benzodithiophene (BDT) or cyclopentadithiophene (CPDT) units and the DFBT unit were synthesized (PBDT–DFBT and PCPDT–DFBT). We found that the DTP based polymer PDTP–DFBT shows significantly improved solubility and processability compared to the BDT or CPDT based polymers. Consequently, very high molecular weight and soluble PDTP–DFBT can be obtained with less bulky side chains. Interestingly, PDTP–DF...

Synthesis of 5H-Dithieno[3,2-b:2′,3′-d]pyran as an Electron-Rich Building Block for Donor–Acceptor Type Low-Bandgap Polymers

We describe the detailed synthesis and characterization of an electron-rich building block, dithienopyran (DTP), and its application as a donor unit in low-bandgap conjugated polymers. The electron-donating property of the DTP unit was found to be the strongest among the most frequently used donor units such as benzodithiophene (BDT) or cyclopentadithiophene (CPDT) units. When the DTP unit was polymerized with the strongly electron-deficient difluorobenzothiadiazole (DFBT) unit, a regiorandom polymer (PDTP–DFBT, bandgap = 1.38 eV) was obtained. For comparison with the DTP unit, polymers containing alternating benzodithiophene (BDT) or cyclopentadithiophene (CPDT) units and the DFBT unit were synthesized (PBDT–DFBT and PCPDT–DFBT). We found that the DTP based polymer PDTP–DFBT shows significantly improved solubility and processability compared to the BDT or CPDT based polymers. Consequently, very high molecular weight and soluble PDTP–DFBT can be obtained with less bulky side chains. Interestingly, PDTP–DFBT shows excellent performance in bulk-heterojunction solar cells with power conversion efficiencies reaching 8.0%, which is significantly higher than PBDT–DFBT and PCPDT–DFBT based devices. This study demonstrates that DTP is a promising building block for high-performance solar cell materials.

New Semiconductors Based on 2,2′-Ethyne-1,2-diylbis[3-(alk-1-yn-1-yl)thiophene] for Organic Opto-Electronics

We report the synthesis and properties of three novel acetylenic materials based on the new electron-rich building block, 2,2′-ethyne-1,2-diylbis[3-(alk-1-yn-1-yl)thiophene] (EBT). The synthesis of this new nonacene core is efficient and straightforward, and variation among n-hexyl, n-tetradecyl, and 2-ethylhexyl substituents substantially impacts the materials properties. Appending 2-ethylhexyl substituted diketopyrrolopyrrole (DPP) units to either terminus of the EBT core yields a series of low band gap molecules that are characterized in detail by a range of experimental microstructure and electronic structure probes and by density functional theory (DFT) computation. Detailed morphology/microstructure characterization of spin-cast films by X-ray diffraction and AFM reveals instructive microstructure and electronic/photovoltaic response relationships in both organic field-effect transistors and bulk-heterojunction organic photovoltaic cells. Thus, the former devices exhibit hole mobilities (μh) as larg...

Benzotrithiophene - A Planar, Electron-Rich Building Block for Organic Semiconductors

Several functionalized benzo[1,2-b:3,4-b':5,6-d'']trithiophenes have been synthesized and characterized. The fully planar and highly electron-rich material shows great promise as the donor constituent in donor-acceptor type copolymers for use in organic electronics. As a proof of concept, a copolymer with the electron acceptor, 2,1,3-benzothiadiazole, has been prepared. Side-chain modifications have been employed to adjust both the electron-rich character of the monomer and the solubility and processability of the polymer.

Superamphiphiles Based on Directional Charge‐Transfer Interactions: From Supramolecular Engineering to Well‐Defined Nanostructures

Superamphiphiles are amphiphiles that are formed on the basis of noncovalent interactions, which may include p–p interactions, hydrogen bonding, charge-transfer interactions, and electrostatic interactions. Superamphiphiles with various architectures can be fabricated, and they can be either small organic molecules or polymers. Because superamphiphiles are synthesized through noncovalent interactions, time-consuming organic synthesis can be avoided to some extent. In addition, building blocks with functional moieties, can be easily incorporated into the superamphiphiles, thus allowing for the fabrication of functional supramolecular nanostructures. Among the various noncovalent interactions that can be used as driving forces for the fabrication of superamphiphiles, chargetransfer interactions between electron-deficient and electron-rich building blocks are especially attractive. The face-to-face packing mode in the charge-transfer complex facilitates the formation of one-dimensional nanostructures. An interesting aspect is that some charge-transfer complexes are highly directional. For example, naphthalene diimide and naphthalene prefer a face-centered packing arrangement, in which the long axes of the two aromatic rings are nearly parallel. Using this unique feature, we attempted to employ this directional charge-transfer interaction to fabricate superamphiphiles of various architectures and to

Quaterthiophenediphosphonic acid (QDP): a rigid, electron-rich building block for zirconium-based multilayers

Quaterthiophenediphosphonic acid (QDP): a rigid, electron-rich building block for zirconium-based multilayers