Since the report of the first diketopyrrolopyrrole (DPP)-based polymer semiconductor, such polymers have received considerable attention as a promising candidate for high-performance polymer semiconductors in organic thin-film transistors (OTFTs). This Progress Report summarizes the advances in the molecular design of high-mobility DPP-based polymers reported in the last few years, especially focusing on the molecular design of these polymers in respect of tuning the backbone and side chains, and discussing the influences of structural modification of the backbone and side chains on the properties and device performance of corresponding DPP-based polymers. This provides insights for the development of new and high-mobility polymer semiconductors.

A new diketopyrrolopyrrole-based π-conjugated copolymer (PDPP5T) with high molecular weight has been synthesized by Stille coupling polymerization of 3,6-bis(5-bromothiophen-2-yl)-2,5-bis(2-octyldodecyl)pyrrolo-[3,4-c]pyrrole-1,4(2H,5H)-dione with α,α′-bis(trimethylstannyl)-terthiophene. Its hole mobility without thermal annealing reaches 1.08 cm2 V–1 s–1, and a higher hole mobility of 3.46 cm2 V–1 s–1 is obtained annealed at 200 °C directly in an air atmosphere. This indicates that introducing a longer β-unsubstituted quinquethiophene (5T) unit into the main-chain of DPP-oligothiophene copolymer produces much pronounced p-type behavior and also reduces the steric hindrance of the bulk side-chain groups, which is favorable to enhance the molecular ordering capability at low temperatures and improve the organic thin-film transistors (OTFT) performances. This work demonstrates that PDPP5T is a promising material that can be applied to the cost-effective and large-scale production of OTFTs.

Two new diketopyrrolopyrrole-based π-conjugated copolymers (PDPP6T and PDPP7T) have been synthesized by Stille coupling polymerization of 3,6-bis(5′bromo-[2,2′-bithiophen]-5-yl)-2,5-bis(2-octyldodecyl)pyrrolo-[ 3 , 4 -c ] p y r r o l e -1 , 4 ( 2 H , 5 H ) -d i o n e w i t h α , α ′ -b i s-( t r i m e t h y l s t a n n y l ) -b i t h i o p h e n e a n d α , α ′ -b i s -(trimethylstannyl)-terthiophene, respectively.The impressive high mobility of 3.94 cm 2 V −1 s −1 for the polymer with sextetthiophene (6T) and of 2.82 cm 2 V −1 s −1 for polymer with septetthiophene (7T) is acquired. It is found that the introduction of longer β-unsubstituted oliogothiophene unit in DPP-based copolymers has a great influence on the molecular weight and solubility of the DPP-oligothiophene copolymers that finally affects the organic thin-film transistor (OTFT) performances, indicating that a suitable number of thiophene group in β-unsubstituted oligothiophene exists for such a kind of copolymer to exhibit the best OTFT performances. This work also reveals the significance in the design of D−A copolymers for OTFTs through regulating the balance between π−π stacking of intermolecular chains and molecular weight as well as solubility of the rigid main chain.

The widespread use of electrically conductive metal−organic frameworks (EC-MOFs) in high-performance devices is limited by the lack of facile methods for synthesizing large-area thin films on the desired substrates. Herein, we propose a spincoating interfacial self-assembly approach to in situ synthesize high-quality centimeter-sized copper benzenehexathiol (Cu-BHT) MOFs on diverse substrates in only 5 s. The film thickness (ranging from 5 to 35 nm) and surface morphology can be precisely tuned by controlling the reaction time. The gas sensor based on the 10 nm thick Cu-BHT film exhibits a low limit of detection (0.23 ppm) and high selectivity value (>30) in sensing NH 3 at ultralow driving voltages (0.01 V). Moreover, the Cu-BHT films retain their initial sensor performance after 1000 repetitive bending cycles at a bending radius of 3 mm. Density functional theory calculations suggest that Cu 2c sites induced by crystal particles on the film surface can improve the sensing performance. This facile and ultrafast approach for in situ synthesis of large-area EC-MOF films on diverse substrates with tunable thickness on a nanometer scale should facilitate application of EC-MOFs in flexible electronic device arrays.

For donor-acceptor conjugated polymers, it is an effective strategy to improve their electron mobilities by introducing electron-withdrawing groups (EWGs, such as F, Cl, or CF 3 ) into the polymer backbone. However, the introduction of different EWGs always requires a different synthetic approach, leading to additional arduous work. Here, an effective two-step method is developed to obtain EWG substituted bay-annulated indigo (BAI) units. This method is effective to introduce various EWGs (F, Cl, or CF 3 ) into BAI at different substituted positions. Based on this method, EWG substituted BAI acceptors, including 2FBAI, 2ClBAI, and 2CF 3 BAI, are reported for the first time. Furthermore, four polymers of PBAI-V, P2FBAI-V, P2ClBAI-V, and P4OBAI-V are developed. All the polymers show ambipolar transport properties. Particularly, P2ClBAI-V exhibits remarkable hole and electron mobilities of 4.04 and 1.46 cm 2 V −1 s −1 , respectively. These mobilities are among the highest values for BAI-based polymers.

This work illustrates an effective side-chain modification approach using amide functional groups to induce aqueous electroactivity to ProDOT-based electrochromic polymers.

A carbon-based, bifunctional metal-free water splitting electrocatalyst is prepared using a nitrogen-enriched polydopamine analogue to produce defect-rich porous carbon, which exhibits superb catalytic activities for both the HER and the OER.

www.rsc.org/ packing for P2 during spin-coating. Further improved performances were obtained by introducing two thiophene units into the polymer backbone to give P3, due to closer π−π stacking, in-plane π−stacking alignment in thin film and a higher HOMO energy level. Therefore, optimized device performance was realized through subtle modification of the polymer structure, including both main chain and side chain, which provides an insight into structure-property relationships for high-mobility polymer semiconductors.