Improving Photovoltaic Performance of the Linear A-Ar-A-type Small Molecules with Diketopyrropyrrole Arms by Tuning the Linkage Position of the Anthracene Core

Synthesis, Characterization and Luminescent Properties of Anthracen- or Pyrene-Based Coumarin Derivatives

Three anthracen- or pyrene-based coumarin derivatives have been successfully synthesized and characterized by EA, IR and ¹H NMR. The photophysical properties of all derivatives were investigated by UV-Vis and photoluminescence spectroscopic analysis. Their thermal stabilities were demonstrated by TGA. These compounds exhibit strong blue mission under ultraviolet light excitation and have potential possible to explore organic electroluminescent materials. The vacuum-processed doped devices with a configuration of ITO/TAPC (20 nm)/TBADN: b1 (x wt%, 30 nm)/TPBi (50 nm)/Liq (2 nm)/Al (150 nm) was fabricated, in which the devices based on b1 exhibited the best electroluminescence performance with a maximum brightness of 8165 cd/m² and a maximum luminous efficiencies of 6.13 cd/A and a maximum external quantum efficiency (EQE) of 2.75%.

Design of Diketopyrrolopyrrole (DPP)-Based Small Molecules for Organic-Solar-Cell Applications

After the first report in 2008, diketopyrrolopyrrole (DPP)-based small-molecule photovoltaic materials have been intensively explored. The power conversion efficiencies (PCEs) for the DPP-based small-molecule donors have been improved up to 8%. Furthermore, through judicious structure modification, DPP-based small molecules can also be converted into electron-acceptor materials, and, recently, some exciting progress has been achieved. The development of DPP-based photovoltaic small molecules is summarized here, and the photovoltaic performance is discussed in relation to structural modifications, such as the variations of donor-acceptor building blocks, alkyl substitutions, and the type of conjugated bridges, as well as end-capped groups. It is expected that the discussion will provide a guideline in the exploration of novel and promising DPP-containing photovoltaic small molecules.

Photovoltaic Small Molecules of TPA(FxBT-T-Cz)3: Tuning Open-Circuit Voltage over 1.0 V for Their Organic Solar Cells by Increasing Fluorine Substitution

To simultaneously improve both open-circuit voltage (V_oc) and short-circuit current density (J_sc) for organic solar cells, a novel D(A-π-Ar)₃ type of photovoltaic small molecules of TPA(F_xBT-T-3Cz)₃ was designed and synthesized, which contain central triphenylamine (TPA), terminal carbazole (Cz), armed fluorine-substituted benzothiadiazole (F_xBT, where x = 1 or 2), and bridged thiophene (T) units. A narrowed ultraviolet-visible absorption and a decreasing highest occupied molecular orbital energy level were observed from TPA(F₁BT-T-3Cz)₃ to TPA(F₂BT-T-3Cz)₃ with increasing fluorine substitution. However, the TPA(F₂BT-T-3Cz)₃/PC₇₁BM-based solar devices showed a rising V_oc of 1.01 V and an enhanced J_sc of 10.84 mA cm^-2 as well as a comparable power conversion efficiency of 4.81% in comparison to the TPA(F₁BT-T-3Cz)₃/PC₇₁BM-based devices. Furthermore, in comparison to the parent TPA(BT-T-3Cz)₃ molecule without fluorine substitution, the fluorine-substituted TPA(F_xBT-T-3Cz)₃ molecules exhibited significantly incremental V_oc and J_sc values in their bulk heterojunction organic solar cells, owing to fluorine incorporation in the electron-deficient benzothiadiazole unit.

Direct C–H arylation for various Ar-cored diketopyrrolopyrrole containing small molecules in solution-processed field-effect transistors

D–A–π–A–D small molecules Ar(DPPT₂)₂ are designed and synthesized by direct (hetero) C–H arylation, with hole mobility as high as 0.12 cm² V⁻¹ s⁻¹.

Conjugated terpolymers synthesized by incorporating anthracene units into the backbones of the diketopyrrolopyrrole-based polymers as electron donors for photovoltaic cells

Three new conjugated D–A terpolymers PADPP1, PADPP2 and PADPP3, which contain diketopyrrolopyrrole (DPP) as electron acceptors and thiophene/anthracene as electron donors for photovoltaic cells, are described.