ZDL

A series of cross-linkable bipolar host materials containing carbazole (donor, D) and 1,2,4-triazole (acceptor, A) were designed and synthesized. The host materials with styryl groups can be thermally cross-linked by curing at 172–190 °C without any polymerization initiator. Excellent solvent resistance was observed for all the host materials, which is beneficial for the preparation of subsequent functional layers by solution processes. The highest occupied molecular orbital energy levels of 5.55, 5.58 and 5.54 eV are estimated for these host materials, which indicates low injection barrier from the hole transport layer. A current efficiency of 15.3 cd A^–1 and an external quantum efficiency of 4.6 % were achieved for solution-processed Ir(mppy)₃-based OLEDs by using the cross-linkable host material.

A series of cross-linkable bipolar host materials containing carbazole donor and 1,2,4-triazole acceptor were designed and synthesized. The host materials with styryl groups can be thermally cross-linked without any polymerization initiator, and all showed excellent solvent resistance. The calculated HOMOs indicate low injection barrier from the hole transport layer. A current efficiency of 15.3 cd A^–1 and EQE of 4.6 % were achieved for solution-processed Ir(mppy)₃-based OLEDs.

The synthesis, photophysical and electrochemical properties, and photovoltaic performances in dye-sensitized solar cells (DSSCs) of five new metal-free organic sensitizers with a carbazole moiety as the electron donor are reported. The compounds contain a thiophene at various positions and a cyanoacrylic acid unit as the electron acceptor. The position of the thiophene moiety affected both the photophysical and electrochemical properties, leading to conversion efficiencies of 1.44 to 4.57 % under AM 1.5 solar conditions (100 mW cm^–2). The best performance and longest electron lifetime were found when a thiophene was located on both donor and acceptor sites. The DSSC showed a short-circuit current (J_sc) of 8.59 mA/cm², an open-circuit photovoltage (V_oc) of 0.75 V, and a fill factor (FF) of 0.71. The position of the π-conjugated bridges not only affects the absorption spectra and the energy levels of the sensitizers, but also adjusts the electron lifetime.

Five new carbazole-based dyes were synthesized. Whereas redshifted spectra can be achieved by inserting a thiophene next to the acceptor, the inclusion of a thiophene as part of the donor causes hyperchromicity but almost no shift in λ_max. The power conversion efficiency of the DSSCs depends on the position of the thiophene.

We report herein general synthetic routes to novel TEG-functionalized DPP-based co-polymers (TEG = triethylene glycol; DPP = diketopyrrolopyrrole) that display alternating TEG-substituted DPP moieties with various functionalized donor units; donor units contain moieties such as polythiophene segments decorated with thermocleavable tertiary esters or additional TEG chains and alkoxy-substituted benzodithiophenes. The synthetic approaches are based on Stille coupling chemistry or, for the first time for TEG-substituted DPP-based polymers, on direct heteroarylation polymerizations. Spectroscopic and electrochemical characterization as well as preliminary tests in photovoltaic cells are also reported.

Synthetic routes to DPP-based (DPP = diketopyrrolopyrrole) copolymers bearing pendant TEG (TEG = triethylene glycol) chains and variously functionalized side chains have been developed. These are based on Stille couplings and, for the first time for TEG-substituted DPP polymers, on direct heteroarylation polymerization. Spectroscopic and electrochemical characterization as well as preliminary tests in photovoltaic cells are reported.

Benzopyrazinoisoindigo, a pigment reported 40 years ago, should be a good candidate for n-type semiconductors if the reported structure is correct. Reinvestigation of this molecule revealed that it is actually (4H,4′H)-benzopyrazinoisoindigo, which could be considered as the reduced form of benzopyrazinoisoindigo, and hence, it is a good candidate for p-type semiconductors. The route toward the synthesis of this molecule was optimized, and a mechanism was accordingly proposed. A field-effect transistor based on this material showed a hole mobility up to 2.5 × 10^–2 cm² V^–1 s^–1.

An expedient route for the synthesis of unexpectedly alkylated (4H,4′H)-benzopyrazinoisoindigo is developed, which also clarifies the previously reported structure. A mechanism is accordingly proposed. A field-effect transistor based on this material shows a hole mobility up to 2.5 × 10^–2 cm² V^–1 s^–1.