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C-C bond forming reactions are central to the construction of π-conjugated polymers. Classical C-C bond forming reactions such as the Stille and Suzuki coupling reactions have been widely used in the past for this purpose. More recently, direct (hetero)arylation polymerization (DHAP) has earned a place in the spotlight with an increasing number of π-conjugated polymers being produced using this atom-economic and more sustainable chemistry. As semiconductors in organic electronics, the device performances of the polymers made by DHAP are of great interest and importance. This review compares the device performances of some representative π-conjugated polymers made using the DHAP method with those made using the conventional C-C bond forming reactions when they are used as semiconductors in organic thin film transistors (OTFTs) and organic photovoltaics (OPVs).

Flexible temperature sensors based on π–conjugated polymers are well‐suited for diverse applications, including food packaging and human health monitoring. Herein, novel dihydropyrazine (DHP)‐based polymers designed for the development of flexible temperature sensors are introduced. The DHP‐based polymers are synthesized via direct arylation polymerization, eliminating toxic byproducts. Polymers with carboxylate potassium salt side chains, which exhibit high solubility in green solvents like water and alcohol are obtained via post‐polymerization hydrolysis of carboxylate ester chains. Furthermore, a post‐deposition treatment converts the carboxylate potassium salt side chains into carboxylic acid side chains, resulting in highly solvent‐resistant polymers. Notably, these DHP‐based polymers exhibit moderate electrical conductivity in the range of ≈10−4 to 10−1 S cm−1 without the need for additional dopants. Resistor‐type temperature sensors based on the self‐doped DHP‐based polymers, processed with ethylene glycol (EG) on flexible polyethylene terephthalate (PET) substrates via blade coating, demonstrate an impressive temperature coefficient of resistance (TCR) of up to −1.5% °C−1 (20–60 °C) and outstanding long‐term stability under ambient conditions. This work presents a well‐founded design of π–conjugated polymers that simultaneously fulfill performance, stability, processability, and cost criteria, paving the way for practical applications of flexible and printable temperature sensors. [ABSTRACT FROM AUTHOR]

Organic semiconductors inherently have a low dielectric constant and hence high exciton binding energy, which is largely responsible for the rather low power conversion efficiency of organic solar cells as well as the requirements to achieve delicate bulk‐heterojunction nanophase separation in the active layer. In this study, methyl acrylate as a weakly electron‐withdrawing side chain for the electron rich thiophene to prepare a new building block, methyl thiophene‐3‐acrylate (TA), with increased polarity is used. A wide bandgap polymer PBDT‐TA synthesized using TA and a benzodithiophene (BDT) monomer shows increased dielectric constant and reduced exciton binding energy compared to the analogous polymer PBDT‐TC, which is made of BDT and methyl thiophene‐3‐carboxylate (TC). An organic solar cell device based on PBDT‐TA:ITIC also achieves a higher power conversion efficiency of 10.47% than that of the PBDT‐TC:ITIC based solar cell (9.68%). This work demonstrates the effectiveness of using acrylate side chains to increase the dielectric constant, reduce the exciton binding energy, and enhance the solar cell efficiency of polymer semiconductors. [ABSTRACT FROM AUTHOR]

A series of donor‐acceptor polymers, namely PTEB, PMEB, PEEB, and PPEB, are designed and synthesized for temperature sensing. The polymers are composed of hemi‐isoindigo as the acceptor unit, 3,3″‐bis(dodecyloxy)‐2,2″‐bithiophene as the donor unit, and thiophene as the spacer unit. Carbamate solubilizing side chains are used to increase the solubility of the polymers in a green solvent anisole. Furthermore, the carbamate side chains can be thermally removed to form solvent‐resistant polymers PTNB, PMNB, PENB, and PPNB, respectively. The removal of carbamate side chains also helps to elevate the highest occupied molecular orbital energy level of the polymer, thereby promoting p‐doping. PMNB, PENB, and PPNB films are doped with 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ) and used for fabricating temperature sensors on flexible polyethylene terephthalate substrates. The sensors exhibit high temperature coefficient of resistance (TCR) of up to −1.92 (±0.125)% °C−1 at 20–60 °C. This is the highest TCR achieved to date for resistor‐type temperature sensors using a non‐composite single conductive polymer. High sensitivity, green solvent processability, and mechanical flexibility make these temperature sensors promising for use in low‐cost, ubiquitous applications. [ABSTRACT FROM AUTHOR]

A novel donor–acceptor (D‐A) conjugated polymer, poly[bis(2‐ethylhexyl)3‐(3′′,4′‐bis(dodecyloxy)‐[2,2′:5′,2′′‐terthiophen]‐5‐yl)‐1,4‐dioxo‐6‐(thiophen‐2‐yl)pyrrolo[3,4‐c]pyrrole‐2,5(1H,4H)‐dicarboxylate] (PDEB), comprising an electron‐accepting carbamate side‐chain bearing thiophene‐flanked diketopyrrolopyrrole (DPPTh) and an electron‐donating 3,3′‐bis(dodecyloxy)‐2,2′‐bithiophene (C12‐BTO) is synthesized. The carbamate side‐chains in this polymer can be thermally removed at a moderate temperature, forming an insoluble polymer poly[3‐(3″,4′‐bis(dodecyloxy)‐[2,2′:5′,2″‐terthiophen]‐5‐yl)‐6‐(thiophen‐2‐yl)‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione] (PDNB) with high solvent resistance. PDNB has a high highest occupied molecular orbital energy level of −4.68 eV and a narrow band gap of 1.05 eV, which makes it dopable by HCl to form a stable conductive polymer PDNB:HCl with moderate conductivity of 0.24 S cm–1. A chemiresistive sensor based on PDNB:HCl can distinguish ten common volatile organic liquids with unique current–time profiles under a low operation voltage of 1 V. Importantly, a single sensor can be used many times and remain functional over a long period of time in air, indicating its extraordinary operational and environmental stability. The results demonstrate that PDNB is a promising material for reusable chemiresistive sensors. [ABSTRACT FROM AUTHOR]

Self-aligned printing is a recently developed bottom-up printing technique which utilizes the unique droplet motion on heterogeneous surfaces to define sub-100-nm critical features and surpasses the resolution which can commonly be achieved by direct printing by two orders of magnitude. Here we extend this method, which was originally implemented with conductive polymer inks, to fabrication of functional conductive nanostructures with gold nanoparticle ink. We also designed a configuration where the ink was printed between two lithographically defined patterns to facilitate the study of the channel formation. Channel lengths from 4 μm down to 60 nm were achieved by controlling the surface tension and drying time of the ink. A fluid dynamical model is presented to explain the mechanism by which the channel forms in the self-aligned printing technique. Field-effect transistors fabricated using gold self-aligned printed source-drain electrodes exhibit significantly improved output currents than those using conducting polymers. Unambiguous evidence for the submicrometer channel dimension is obtained by imaging the potential drop along the channel using scanning Kelvin probe microscopy. [ABSTRACT FROM AUTHOR]

A donor-acceptor polymer of (3 E,7 E)-3,7-bis(2-oxoindolin-3-ylidene)benzo[1,2- b : 4,5- b′]difuran-2,6(3 H,7 H)-dione (IBDF) and bithiophene (BT) exhibits typical ambipolar charge transport behaviour in organic thin film transistors. Using the electron rich triphenylamine as an end capping group, a notable suppression of hole transport is observed. This interesting phenomenon is accounted for by the hole trapping effect of the triphenylamine end-capper. Thus, this study provides a novel and facile approach to tuning the charge carrier polarity of a polymer semiconductor from ambipolar to n-type dominant. [ABSTRACT FROM AUTHOR]

Three thiophene- S, S-dioxidized indophenine (IDTO) isomers, 3 a ( E, E, E), 3 b ( Z, E, E), and 3 c ( Z, E, Z), were synthesized by oxidation of an indophenine compound. 3 b and 3 c could be converted into the most-stable 3 a by heating at 110 °C. An IDTO-containing conjugated polymer, PIDTOTT, was prepared using 3 a as a comonomer through a Stille coupling reaction, and it possesses a narrow band gap and low energy levels. In organic field effect transistors (OFETs), PIDTOTT exhibited unipolar n-type semiconductor characteristics with unexpectedly high electron mobility (up to 0.14 cm2 V−1 s−1), despite its rather disordered chain packing. [ABSTRACT FROM AUTHOR]

Two donor–acceptor (D–A) conjugated polymers, PINDFTT and PINDFBT, based on a novel electron acceptor, (3E,8E)-3,8-bis(2-oxoindolin-3-ylidene)naphtho-[1,2-b:5,6-b′]difuran-2,7(3H,8H)-dione (INDF), are synthesized for solution processed organic thin-film transistors. Both polymers exhibited highly balanced ambipolar characteristics with hole and electron mobilities up to 0.51 cm2 V−1 s−1 and 0.50 cm2 V−1 s−1, respectively. [ABSTRACT FROM AUTHOR]

The article focuses on a study regarding large modulation of charge anisotropy by controlling the alignment of #03C0;-&#x03C0 stacks in diketopyrrolopyrrole-based polymers. It mentions the use of optoelectronic devices such as photovoltaic cells and thin film field effect transistors (FETs) for semiconducting polymers. It also mentions that semiconducting polymer thin films enhance crystallinity.

A novel acceptor, (3E,7E)-3,7-bis(2-oxoindolin-3-ylidene)-5,7-dihydropyrrolo[2,3-f]indole-2,6(1H,3H)-dione, was reported. Donor–acceptor (D–A) polymer semiconductors using this new building block showed high ambipolar charge transport performance with hole and electron mobilities up to 0.19 and 0.09 cm2 V−1 s−1, respectively, in thin film transistors. [ABSTRACT FROM AUTHOR]

(3E,7E)-3,7-Bis(2-oxoindolin-3-ylidene)benzo[1,2-b:4,5-b′]difuran-2,6(3H,7H)-dione (IBDF) was used as a new electron-acceptor building block for polymer semiconductors with very low-lying energy levels. A copolymer of IBDF and thiophene showed stable electron transport performance in thin film transistors. [ABSTRACT FROM AUTHOR]

A series of electron-acceptor polymers, copolymers and blends were used in all-polymer BHJ photodetectors and the effect of acceptor compositions on the key device parameters of dark current density and photocurrent was investigated. Compared with acceptor polymers and polymer blends, the devices based on acceptor copolymer showed lowered dark current and higher photocurrent, due to optimal molecular stacking and morphology of the BHJ active layer. The acceptor blends tend to cause a large phase separation and rough surface of the active layer, thus leading to a low detectivity of the device. Among all the acceptor compositions studied in this work, the all-polymer BHJ photodetector based on a donor polymer ( PolyD ) and an acceptor copolymer ( PolyAA′50 ) exhibited the highest specific detectivity of over 10 12 Jones in the spectral region of 320–980 nm under −0.1 V bias. [ABSTRACT FROM AUTHOR]

We studied the vertical and lateral charge transport characteristics of a diketopyrrolopyrrole polymer donor (D)–PC61BM acceptor (A) system by measuring the space charge limited current (SCLC) mobility and field-effect mobility respectively. It was found that with an increase in annealing temperature, the SCLC hole mobility decreased for the pure polymer (PDBFBT) but increased for the PDBFBT:PC61BM blends, which could be explained by changes in the crystallinity and crystal orientation (edge-on versus face-on). The pure PDBFBT and most blend films showed the maximum field-effect hole mobility (µh) when annealed at 100°C, which then declined as the annealing temperature was further increased. Surprisingly, the D/A = 1/1 blend films annealed at high temperatures exhibited an abrupt increase in the field-effect µh. This unusual phenomenon was interpreted by the antiplasticization effect of PC61BM, which promoted the molecular organization of the polymer. The effect of annealing on the carrier mobility was further correlated with the performance of inverted organic solar cell devices with the PDBFBT:PC61BM blend (D/A = 1/3). Thermal annealing at high temperatures (>100°C) was found to obstruct electron transport and cause the device performance to significantly deteriorate. [ABSTRACT FROM AUTHOR]

Highlights: [•] A p-type polymer semiconductor with exceptionally high SCLC mobility (2.3×10−2 cm2 V−1s−1) is reported. [•] Solution-processed BHJ OSCs based on this polymer and PC61BM achieved a PCE of 4.53%. [•] We demonstrate the benefits of high mobility materials as they relate to active layer thickness and fill factor. [ABSTRACT FROM AUTHOR]

Two new π-conjugated polymers with donor backbone and π-conjugated indolin-2-one side chains, PBDTTI and PBDTTIF, are designed and synthesized as wide bandgap donors for non-fullerene acceptor-based organic solar cells (OSCs). The monomers containing electron accepting indolin-2-one side chains, (Z)-3-((2,5-dibromothiophen-3-yl) methylene)-1-methylindolin-2-one (M1) and (Z)-3-((2,5-dibromothiophen-3-yl) methylene)-5-fluoro-1-methylindolin-2-one (M2), can be easily synthesized via Knoevenagel condensation between 2,5-dibromothiophene-3-carbaldehyde and 2-oxindole or 5-fluoro-2-oxindole, respectively. Stille coupling polymerization of the electron donating benzodithiophene (BDT)-containing monomer 1,1′-[4,8-bis [5-(2-ethylhexyl)-2-thienyl]benzo [1,2- b :4,5- b ′]dithiophene-2,6-diyl]bis [1,1,1-trimethylstannane] and M1 or M2 produced PBDTTI or PBDTTIF, respectively. The strong electron accepting π-conjugated 1-methylindolin-2-one and 5-fluoro-1-methylindolin-2-one side chains can achieve low-lying HOMO energy levels of −5.59 eV for PBDTTI and −5.60 eV for PBDTTIF, which is beneficial for realizing high open circuit voltage (V OC) of the resulting OSCs. On the other hand, since the electron acceptor units are on the side chains, the polymer backbone containing only electron donor units could maintain wide bandgaps of 1.91 eV and 1.89 eV for PBDTTI and PBDTTIF, respectively. When PBDTTI and PBDTTIF were used as donors and a small bandgap non-full acceptor ITIC as an acceptor, the resulting OSCs devices achieved V OC of 0.97 and 1.00 V, short circuit current densities (J SC) of 15.60 and 13.70 mAcm-2, and fill factors (FF) of 0.60 and 0.59, resulting in power conversion efficiencies of 8.00 and 7.70%, respectively. [Display omitted] • Two new donor-backbone and acceptor-side chain polymer donors are synthesized. • Low frontier energy levels and wide bandgap are achieved. • Organic solar cells using these polymer donors showed promising performance. [ABSTRACT FROM AUTHOR]

Abstract: Rather consistent power conversion efficiencies have been achieved in organic solar cells throughout a wide range of active layer thicknesses (∼100nm to ∼800nm) by using a p-type polymer semiconductor with high hole transport mobility (∼1cm2 V−1 s−1) as the donor, and PC61BM as the acceptor. A comparison between standard and inverted device configurations demonstrates that the inverted configuration is more suitable for achieving thicker active layers when a high hole mobility donor is used. We attribute this to the longer hole collection path in the inverted structure, which can benefit from using a high hole mobility material. Our results will be very useful for the development of new semiconductor materials and the design of device structures for more feasible manufacturing of large area OPV devices via high speed roll-to-roll printing processes. [Copyright &y& Elsevier]