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In this work, P(NDI2OD-T2) was blended with various amounts of PEO, aPP, or iPP to furnish numerous thin films. The morphology of pristine P(NDI2OD-T2) and the blends was investigated by X-ray phot...

Two-dimensional alkylated αβ-TTN and βα-TTN were designed and synthesized. The cross-shaped αβ-TTN and βα-TTN moieties were polymerized to afford two isomeric polymers, Pαβ-TTNFBT40 and Pβα-TTNFBT4...

A first-generation Grubbs catalyst has been shown to not only catalyze the ring opening metathesis polymerization (ROMP) of cyclopropene derivatives but also differentiate E- and Z-double bonds in ...

Two stacking manners, that is, π- and lamellar stacking, are generally found for organic semiconductors, in which the π-stacking occurs between conjugated groups and the lamellar stacking refers to the separation of the conjugated and aliphatic moieties. The stacking principles are yet not well-defined. In this work, extended transition state-natural orbitals for chemical valence (ETS-NOCV), an energy decomposition analysis, is utilized to examine the π- and lamellar stacking for a series of naphthalenetetracarboxylic diimide (R-NDI) crystals. The crucial role of dispersion is validated. The perception that π-stacking is merely determined by the conjugated moiety is challenged. The stacking principles are associated with the closest packing model. Nanoscopic phase separation of conjugated and aliphatic moieties and the formation of lamellar and herringbone motifs in the R-NDIs can thus be clarified. Moreover, the interactions between NDI and the alkyl chain are investigated, revealing that the interactions can be significant, being contradictory to the conventional point of view. Along with R-NDIs, additional organic crystals consisting of various conjugated functionalities and substituents are also investigated by ETS-NOCV. The sampling scope is up to 108 conjugated molecules. The dominant role of dispersion force irrespective of the variation in the conjugated moieties and substituents is further confirmed. It is envisaged that the established principles are applicable to other organic semiconductors. The perspective toward the π- and lamellar stacking might be modified, paving the way for ultimate morphological control.

A new class of additive materials bis(pentafluorophenyl) diesters (BFEs) where the two pentafluorophenyl (C6F5) moieties are attached at the both ends of a linear aliphatic chain with tunable tether lengths (BF5, BF7, and BF13) were designed and synthesized. In the presence of the BF7 to restrict the migration of fullerene by hand-grabbing-like supramolecular interactions induced between the C6F5 groups and the surface of fullerene, the P3HT:PC61BM:BF7 device showed stable device characteristics after thermal heating at 150 oC for 25 h. The morphologies of the active layers were systematically investigated by OM, GISAXS, and AFM. The tether length between the two C6F5 groups plays a pivotal role in controlling the intermolecular attractions. BF13 with long and flexible tether might form a BF13-fullerene sandwich complex that fails to prevent fullerene’s movement and aggregation, while BF5 with too short tether length decreases the possibility of interactions between the C6F5 groups and the fullerenes. BF7...

ETS–NOCV charge and bond energy analyses have been carried out for a broad range of transition-metal carbonyl complexes L–[M], comprising different ligand classes, transition metals, and coordination geometries. The resulting electronic redistributions are visually assigned to σ donation, π backbonding, and related interactions. We propose a Hirshfeld partitioning of these electronic redistributions to afford the corresponding charge flow contributions Δqσ, Δqπ, etc. Taken together, a detailed picture of the dative bonding arises, in terms of both energetics and the extent of σ-electron donation and π-electron backbonding. The charge flows Δqσ and Δqπ appropriately quantify trends in the ligand σ-donor and π-acceptor abilities and are transferable across the transition-metal complexes studied and thus promise to be suitable descriptors for ligand knowledge bases. As a case in point, the TEP is well reproduced by the calculated νCO(A1) frequencies and is 3 times more strongly affected by Δqσ than by Δqπ, w...

Aqueous palladium-catalyzed direct arylation polymerization (DArP) of 2-bromothiophene derivatives 6-(2-(2-bromothiophen-3-yl)ethoxy)hexyl trimethylammonium bromide (T1) and 4-(2-(2-bromothien-3-yl)ethoxy)butylsulfonate (T2) is achieved. The supporting ligand, triphenylphosphine-3,3',3''-trisulfonic acid trisodium salt (m-TPPTs), facilitates DArP of both derivatives; however, its separation from the polymers by dialysis is difficult due to its strong aggregation in water and N,N-dimethylacetamide (DMAc). This is supported by dynamic light scattering, gel permeation chromatography (GPC), and single-crystal X-ray crystallography. Pyrimidine-Pd(OAc)2 is utilized in the DArP of T1 to afford PT1 without ligand contamination. Density functional theory calculations to determine the coordinating capability of the carboxylate/pivalic acid/water to palladium indicate the viability of implementing DArP in water. Finally, polyelectrolyte molecular-weight overestimation by GPC in water is attributed to the polyelectrolyte effect. Aggregation of the conjugated polyelectrolytes leads to a contracted hydrodynamic volume, and the molecular weight and dispersity assessed by GPC in DMAc significantly deviate from the actual values. An objective approach to evaluate the molecular weight for conjugated polyelectrolytes requires further development.

A systematic methodology is developed to construct the angular-shaped β-form naphthodithiophene (β-aNDT) core with regiospecific substitution of two alkyl groups at its 4,9- or 5,10-positions via the base-induced double 6π-cyclization of dithienyldieneyne precursors, leading to the two isomeric 4,9-β-aNDT and 5,10-β-aNDT monomers. It is found that a more curved geometry of the β-aNDT units intrinsically increases the solubility and thus the solution-processability of the resultant polymers. Therefore, β-aNDT units are ideal for polymerization with an acceptor-containing monomer without the need for any solubilizing aliphatic side chains, which are considered the insulating portion that jeopardizes charge transport. Based on this consideration, the 4,9- and 5,10-dialkylated β-aNDT monomers are polymerized with the non-alkylated DTFBT acceptor to afford two P4,9-βNDTDTFBT and P5,10-βNDTDTFBT copolymers for head-to-head comparison of the 4,9-inner/5,10-outer isomeric alkylation effect. It is found that 4,9-β-aNDT adopts a twisted conjugated structure due to the intramolecular steric repulsion between the inner branched side chains and the β-hydrogens on the thiophene rings. The slightly twisted 4,9-β-aNDT moiety allows P4,9-βNDTDTFBT to have higher solubility upon polymerization and thus a higher molecular weight, which eventually induces a higher ordered packing structure in the thin film compared to P5,10-βNDTDTFBT. As a result, P4,9-βNDTDTFBT exhibits a higher OFET mobility of 0.18 cm2 V−1 s−1, and the P4,9-βNDTDTFBT:PC71BM-based solar cell device also achieves a higher PCE of 7.23%, which is even better than the corresponding P4,9-αNDTDTFBT-based device.

A nonacylic building block TPTPT with the alternate thiophene and benzene subunits fastened by four bridging methylene groups was connected with various acceptors including diphenylquinoxaline ( QX ), thieno[3,4- c ]pyrrole-4,6(5H)-dione ( TPD ), thieno[3,4- b ]thiophene ( TT ) to afford donor-acceptor (D-A) alternating copolymers - PTPTPTQX , PTPTPTTPD , and PTPTPTTT and random copolymers - PTPTPTQX11 , PTPTPTQX12 , PTPTPTTPD11 , PTPTPTTPD12 , PTPTPTTT11 , and PTPTPTTT12 . The thermal, optical, and electrochemical properties of these copolymers were measured and compared. The random copolymers all have higher glass transition temperature ( T g ) than the corresponding alternating copolymers. ONIOM (our own n-layered integrated molecular orbital and molecular mechanics) calculations suggest that the increase of planarity in the random copolymers arises from the introduction of thiophene units intercalating between donor and acceptor moieties. Bulk heterojunction (BHJ) polymer solar cells (PSCs) were fabricated on the basis of ITO/PEDOT:PSS/polymer:PC 71 BM/Ca/Al device configuration. When the acceptor is QX or TPD , the resultant alternating copolymers performed superior than the random counterparts. When the acceptor is TT , the high content of TT seems to be harmful to the device efficiency, which may relate with the strong quinoidal character of the TT unit. Overall, for the TPTPT core structure, in the used acceptors, the alternating-copolymer arrangement appears to be a better construction manner for the purpose of BHJ PSC applications.

A new tetracyclic 4,9-dialkyl angular-shaped naphthodiselenophene (4,9-α-aNDS) was designed and synthesized. The naphthalene core in 4,9-α-aNDS is formed by the DBU-induced 6π-cyclization of an (E)-1,2-bis(3-(tetradec-1-yn-1-yl)selenophen-2-yl)ethene intermediate followed by the second PtCl2-catalyzed benzannulation. This synthetic protocol allows for incorporating two dodecyl groups regiospecifically at 4,9-positions of the resulting α-aNDS. An ordered supramolecular self-assembly formed via noncovalent selenium–selenium interactions with a short contact of 3.5 A was observed in the single-crystal structure of 4,9-α-aNDS. The distannylated α-aNDS building block was copolymerized with Br-DTFBT and Br-DPP acceptors by Stille cross coupling to form two new donor–acceptor polymers PαNDSDTFBT and PαNDSDPP, respectively. The bottom-gate/top-contact organic field-effect devices using the PαNDSDTFBT and PαNDSDPP semiconductors accomplished superior hole mobility of 3.77 and 2.17 cm2 V–1 s–1, respectively, which ...

Angular-shaped dialkyltetracenedithiophenes (aTDTs) undergo [4+4] photodimerization in solution to form a butterfly-shaped skeleton. This reaction proceeds in a regio- and stereo-selective manner, forming only a single planosymmetric syn-[2,2]-daTDT out of six possible products. The photocycloaddition of aTDTs can take place topochemically in the thin-film state while maintaining regio- and stereo-selectivity. Stronger aliphatic dispersion forces and π–π interactions play important roles in forming the eclipsed dimeric complex that leads to the syn-[2,2]-daTDT isomer.

Isomeric 2,8-distannyl 5,11-didodecyl αβ-TTN (1, tetrathienonaphthalene = TTN) and 2,8-didodecyl 5,11-distannyl αβ-TTN (2) have been designed and successfully synthesized. The naphthalene core structures in αβ-TTNs were constructed by a systematic protocol using PtCl2-catalyzed cyclization followed by oxidative Scholl annulation in good yields. Compared to the one-dimensional naphthodithiophene derivatives, the two-dimensional αβ-TTN molecules showed good solubility, extended conjugation, strong absorptivity, and highly coplanar structures. Compounds 1 and 2 were polymerized with a 5,5'-dibromo-2,2'-bithiophene-based monomer to afford 2,8-αβ-PTTNTT and 5,11-αβ-PTTNTT copolymers. 2,8-αβ-PTTNTT with the α-aNDT moiety in the main chain exhibited a higher hole mobility of 1.26 × 10(-2) cm(2) V(-1) s(-1).

We have designed and synthesized a tricyclic diseleno[3,2-b:2′,3′-d]silole (DSS) wherein the 3,3′-position of a biselenophene is bridged by a dioctylsilyl moiety. The distannylated DSS was copolymerized with a diketopyrrolopyrrole (DPP) acceptor to form a donor–acceptor copolymer PDSSDPP. The thiophene-based dithieno[3,2-b:2′,3′-d]silole (DTS) monomer and its corresponding copolymer PDTSDPP are also prepared as references for investigation of the chalcogen effect. Compared to PDTSDPP, PDSSDPP exhibits a more red-shifted absorption spectrum, a higher-lying HOMO energy level, and closer interchain packing associated with the more polarizable Se atom to induce stronger intermolecular interactions. The selenophene-based PDSSDPP shows a mobility of 2.47 × 10−2 cm2 V−1 s−1, which is nearly one order magnitude higher than the thiophene-based PDTSDPP with a mobility of 3.89 × 10−3 cm2 V−1 s−1. This result suggests that the DSS unit and its polymers are promising for OFET applications.

We present a facile synthesis method to make a new ladder-type heptacyclic dithienobenzofluorene (DTBF) framework, where the central 2,7-fluorene unit is covalently fastened with two external thiophenes via two CC bridges. A dieneyne-containing precursor undergoes DBU-induced double benzannulation to regiospecifically introduce two solubilizing 2-octyldodecyl side chains at 5,10-positions of DTBF. The rigid and coplanar Br-DTBF monomer with sufficient solubility was copolymerized with 5,6-difluoro-4,7-bis(5-(trimethylstannyl)thiophen-2-yl)benzo[c][1,2,5]thiadiazole (Sn-DTFBT) and 5,10-bis(5-(trimethylstannyl)thiophen-2-yl)naphtho[1,2-c:5,6-c′]bis([1,2,5]thiadiazole) (Sn-DTNT) via Stille coupling to furnish two donor–acceptor copolymers, PDTBFFBT and PDTBFNT, respectively. Their thermal, optical, electrochemical, molecular stacking and photovoltaic properties are investigated. PDTBFNT has a higher molecular weight, smaller optical and electrochemical band gaps, and stronger solid-state packing than PDTBFFBT. DFT calculations were carried out to gain insight into the electronic and structural properties of DTBF and its derivatives. Bulk heterojunction solar devices with the ITO/ZnO/polymers:PC71BM/MoO3/Ag configuration were fabricated. By adding 5 vol% diphenyl ether (DPE) as an additive, PDTBFNT:PC71BM and PDTBFFBT:PC71BM devices achieved the power conversion efficiencies of 5.22% and 2.68%, respectively. The superior efficiency of PDTBFNT over PDTBFFBT is attributed to the better LUMO energy alignment between PDTBFNT and PC71BM and the face-on π-stacking of PDTBFNT in the active layer. Moreover, PDTBFNT exhibited a higher field-effect transistor hole mobility of 1.90 × 10−2 cm2 V−1 s−1 than PDTBFFBT with a value of 3.96 × 10−3 cm2 V−1 s−1.

Non-conjugated triethylene glycol (3-EG), tetraethylene glycol (4-EG) and pentaethylene glycol (5-EG) are presented as new cathode modification materials to achieve high-performance inverted-PCSs. By spin-coating from a non-chlorinated solvent, these small molecules can self-assemble on ITO via surface coordination and hydrogen bonding to form an ultra-thin layer. Theoretical simulations reveal that the coordination of oxygen atoms in the EG molecules to indium moieties on the ITO surface is the major mechanism in inducing interfacial dipoles, thereby reducing the work function (WF) of ITO for efficient electron collection. Based on the PBDTTT-EFT:PC71BM blend, the bulk heterojunction device using the 5-EG layer exhibited a higher short-circuit current density (Jsc) of 15.27 mA cm−2, fill factor (FF) of 0.69, and power conversion efficiency (PCE) of 8.46%, which are better than those of the corresponding devices using either inorganic ZnO or non-conjugated poly(ethylene oxide) (PEO) as the cathode buffer layer. More importantly, this simple and expedited strategy is also demonstrated to be universally applicable to various p-type conjugated polymers. The EG oligomers with well-defined chemical structures have the advantages of easy availability, simple processability and good device reproducibility, which are crucial keys for future commercialization using large-scale roll-to-roll production.

A single isomer of fullerene bisadduct, PC61PF, was obtained from commercially available fullerene derivative, PC61BM, in one pot over two steps. The tether-directed remote functionalization approach provided a very simple and fast method to produce a single isomer of fullerene bisadduct with good yield and easy purification. Bulk heterojunction organic solar cells containing the bisadduct was fabricated and tested.

A new polymer PDTFDPP20 based on dithieno[3,2-b:6,7-b′]fluorene (DTF) unit was developed. This polymer with a face-on orientation has achieved a high field-effect mobility up to 5 cm2 V–1 s–1., A ladder-type dithieno[3,2-b:6,7-b′]fluorene (DTF), where the central fluorene is fused with two outer thiophene rings at its 2,3- and 6,7-junctions, is developed. The pentacyclic DTF monomers were polymerized with dithienodiketopyrrolopyrrole (DPP) acceptors to afford three alternating donor–acceptor copolymers PDTFDPP16, PDTFDPP20, and PDTFDPP32 incorporating different aliphatic side chains (R1 group at DTF; R2 group at the DPP moieties). The side-chain variations in the polymers play a significant role in determining not only the intrinsic molecular properties but also the intermolecular packing. As evidenced by the 2-dimensional GIXS measurements, PDTFDPP16 with octyl (R1) and 2-ethylhexyl (R2) side chains tends to align in an edge-on π-stacking orientation, whereas PDTFDPP20 using 2-butyloctyl (R1) and 2-ethylhexyl (R2) adopts a predominately face-on orientation. PDTFDPP32 with the bulkiest 2-butyloctyl (R1) and 2-octyldodecyl (R2) side chains shows a less ordered amorphous character. The OFET device using PDTFDPP20 with a face-on orientation determined by GIXS measurements achieved a high hole-mobility of up to 5 cm2 V–1 s–1. The high rigidity and coplanarity of the DTF motifs play an important role in facilitating intramolecular 1-dimensional charge transport within the polymer backbones. The implementation of main-chain coplanarity and side-chain engineering strategies in this research provides in-depth insights into structure–property relationships for guiding development of high-mobility OFET polymers.

In this work, a combined approach was used to obtain a low-cost material for organic electronics by focusing on inexpensive monomers, short synthetic pathway, high-yielding polymerization method, low waste, and easy scalability. To achieve this, a new material, poly[isoindigo-alt-3,4-ethylenedioxythiophene], was synthesized using direct (hetero)arylation polymerization (DHAP). Only a few synthetic steps are required to obtain this material, and no organometallic intermediates are used. In order to make a bigger step toward a truly inexpensive technology, continuous flow methods were applied for the first time to DHAP. This method helped solving a common problem encountered in conjugated polymers synthesis, namely, batch-to-batch variations. Electronic properties of this polymeric material were evaluated using field effect transistors (μh = 7 × 10-3 cm2·V-1·s-1) and solar cells (η = 3.0%).

A new class of heptacyclic ladder-type terbenzodithiophene (TBDT) structures merging three fused benzodithophenes was developed. Two TBDT conjugated isomers, named as syn-TBDT and anti-TBDT, where the two thienyl rings in the outmost BDT units are in the syn- and anti-fashion, are designed. Two decyl groups are introduced to their 6,13 and 7,14-positions to form four isomeric 6,13-syn-TBDT, 7,14-syn-TBDT, 6,13-anti-TBDT, and 7,14-anti-TBDT structures which are constructed by the DBU-induced 6-benzannulation involving propargyl-allenyl isomerization of the dieneyne moieties in the corresponding precursors followed by 6π-electrocyclization/aromatization, while isomeric TD-syn-TBDT and TD-anti-TBDT with four decyl groups substituted at 6,7,13,14-positions are synthesized via palladium-catalyzed dialkylacetylene insertion/C-H arylation of the corresponding iodobiaryl precursors. The intrinsic properties can be modulated by molecular manipulation of the main-chain and side-chain isomeric structures. anti-TBDT derivatives exhibit higher melting points, larger bandgaps, stronger intermolecular interactions, and higher mobility than the corresponding syn-TBDT analogues. These molecules can be further utilized as building blocks to make various TBDT-based materials for optoelectronic applications.

A series of rhenium trioxo complexes (L-ReO3) was synthesized, characterized, and demonstrated to be active in olefin metathesis. The relationship between perrhenate (ReO4-), perrhenyl (ReO3+), and metathesis-active rhenium complexes (L-ReO3) was elucidated. Their chemical behavior can be tuned through the Lewis acid–base interaction. DFT calculations were performed for the metathesis reaction of L-ReO3 with norbornene, which demonstrates that electron-withdrawing substituents or ligands are beneficial for olefin metathesis activity. Moreover, a rhenium-alkylidene complex was synthesized, which can be activated by B(C6F5)3 to afford an active metathesis catalyst. This system can be regarded as a homogeneous model of the hypothetical species present in the heterogeneous catalytic systems. The findings from the present study are consistent with our previous gas-phase studies and constitute the elucidation of the working principles for the metathesis-active rhenium species on the surface.