Conjugated polymers based on modified benzo[1,2-b:4,5-b′]dithiophene and perylene diimide derivatives: Good optical properties and tunable electrochemical performance

Dithienocoronene diimide (DTCDI)-derived triads for high-performance air-stable, solution-processed balanced ambipolar organic field-effect transistors

Developing ambipolar organic semiconducting materials is essential for use in complementary-like inverters and light-emitting transistors. In this study, three new dithienocoronenediimide (DTCDI)-derived triads, DTCDI-BT, DTCDI-BBT and DTCDI-BNT, were designed and synthesized, in which various sizes of terminal groups, i.e., thiophene (T), benzo[b]thiophene (BT) and naphtha[2,3-b]thiophene (NT) were substituted at the α-positions of the two thiophene rings of DTCDI, respectively. The DFT calculations reveal that the HOMO energy levels of the three triads when compared to that of the parent DTCDI-core (-5.99 eV) are significantly increased to -5.59, -5.59 and -5.45 eV for DTCDI-BT, DTCDI-BBT and DTCDI-BNT, respectively, whereas the LUMO energy levels (-3.07 eV ∼ -3.14 eV) are almost identical with that of the DTCDI-core (-3.10 eV). The results predict that the triads could possess ambipolar transport properties in organic field-effect transistor (OFET) applications. In fact, under an ambient atmosphere, solution-processed bottom-gate top-contact (BGTC) transistors exhibit ambipolar charge transport properties by tuning the HOMOs of the DTCDI-based triads so that they were suitable for hole injection, resulting in balanced maximum electron and hole mobilities of 1.66 × 10-3 and 1.02 × 10-3 cm2 V-1 s-1 for DTCDI-BT, 2.60 × 10-2 and 3.60 × 10-2 cm2 V-1 s-1 for DTCDI-BBT, and 2.43 × 10-3 and 4.15 × 10-3 cm2 V-1 s-1 for DTCDI-BNT, respectively. This is the first time that the DTCDI building block has been used to develop ambipolar small molecular semiconductors, and achieved a device performance comparable to that of the DTCDI-based polymeric semiconductors. In addition, DTCDI-BBT-based complementary-like inverters were made, and the inverter devices operated well in both p-mode and n-mode under ambient conditions. The results show that the DTCDI is a promising π-electron-deficient building block which could be further used to develop ambipolar semiconducting materials for OFET devices.

Microwave-Assisted Classic Ullmann C-C Coupling Polymerization for Acceptor-Acceptor Homopolymers

Developing cheap, clean and atomic-efficient synthetic methodologies for conjugated polymers are always critical for the field of organic electronics. Herein, classic Ullmann coupling polymerization is developed to synthesize a series of Acceptor-Acceptor (A-A) type homopolymers with microwave-assistance, which are supported by nuclear magnetic resonance (NMR), matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF), elemental analysis (EA) and gel permeation chromatography (GPC). The physicochemical properties of these polymers are studied by UV-vis spectroscopy, cyclic voltammetry (CV), thermal gravimetric analysis (TGA), and density functional theory (DFT) calculation. Furthermore, these A-A homopolymers are used as acceptors for all-polymer solar cells (All-PSCs), affording a promising efficiency of 3.08%, which is the highest value for A-A-homopolymer-based organic solar cells.

Synthesis and C-H Functionalization Chemistry of Thiazole-Semicoronenediimides (TsCDIs) and -Coronenediimides (TCDIs)

Coronenediimide (CDI) derivatives have a planar structure, a reasonably high electron affinity, and a rigid and extended delocalized π-system. Therefore, this core and variants thereof may be promising building blocks for the synthesis of electron transport materials. Herein, we have synthesized thiazole-semicoronenediimides (TsCDIs) and -coronenediimides (TCDIs) by a two-step process from a perylenediimide (PDI) precursor. Conditions for C-H arylation and heteroarylation of the thiazole moiety of this core were developed and were successfully used for the synthesis of dimer, triad, and polymeric materials. The optical and electrochemical properties of these materials and their monomers were examined as a function of side-chain modification and π-extension. With their broad optical absorption and low reduction potentials, these materials could be candidates as organic semiconductors for applications in OFETs and as nonfullerene acceptors.

Pentacene based Onsager crosses

A dearomatization/aromatization strategy accesses the tetrahedral (crosslike) pentacene tetramer (tetrakis(4-((6,13-bis(TIPS-ethynyl)pentacen-2-yl)ethynyl)phenyl)silane). This molecular caltrop and one of its derivatives form amorphous thin films, demonstrating the impact of the 3D-tetramerization on the bulk morphology of the otherwise crystalline TIPS-pentacene.

Regular terpolymers with fluorinated bithiophene units for high-performing photovoltaic cells

We demonstrate effective structural control of various electron-donating moieties containing bithiophene (BT) and naphthalene derivatives with 3,3′-difluoro-2,2′-bithiophene in a regular terpolymer system and compare the properties of these polymers with those of the three binary copolymers PDPPNp, PDPPBT, and PDPPFBT.