New triarylamines with high mobility have been identified for p-channel OFET applications: their high ON/OFF ratio proves them to be a promising candidate for circuits and switches.
We designed and synthesized phenanthro[9,10-d]imidazoles
(PIs) in a D–A fashion to achieve a balance of charge carriers.
Solution processable bottom gate–top contact organic field-effect
transistors (OFET) were fabricated using a binary solvent system.
The devices exhibited excellent p-channel characteristics with a high
mobility of 0.70 cm2 V–1 s–1 and an on/off ratio of 107. Frontier molecular orbital
levels and packing modes obtained from computational analysis supported
the observed high mobility of the synthesized PI. Solvatochromism
study of the compounds marked them insensitive toward solvent polarity.
Photophysical behavior of the compounds in tetrahydrofuran/H2O inferred efficient aggregate behavior. Scanning electron microscopy
images of the aggregates in high water content show the formation
of nanoaggregates. Dynamic light scattering experiments suggested
a unimodal distribution of the nanoaggregates. This research work
reports functionalized PIs with excellent OFET performance.
A series of metal-free porphyrin molecules with functionalized triarylamines at the meso-position are designed and synthesized. All the functionalized porphyrins possess good thermal stability and high decomposition temperatures over 422 °C and also exhibited electrochemical reproducibility. The calculated ionization potentials are in the range of −5.01 to -5.42 eV, and electron affinity levels are in between −2.47 and −2.91 eV, which supports stable charge ejection. Organic fieldeffect transistor (OFET) devices with bottom-gate/top-contact architecture are fabricated by a solution-processable technique. OFETs with an active layer of porphyrin with electron-accepting trifluorophenyl groups gave the highest charge carrier mobility of 4.4 cm 2 /Vs and an on/off ratio of 10 7 . The obtained results indicate these compounds to be efficient hole-transporting materials. This research work presents the highest mobilities of the porphyrins reported until now.
Phenanthro[9,imidazole is synthesized by employing Radziszewski method and further functionalized through palladium catalyzed Suzuki cross-coupling reaction. Solution processable organic field-effect transistors (OFETs) are assembled in bottom gate-top contact architecture. A binary solvent system comprising of chloroform/toluene in the ratio of 1/1 is preferred for the deposition of active semiconducting layer. The fabricated devices demonstrated excellent p-type characteristics with a good mobility, high ON/OFF ratio of 10 9 and a minimum threshold voltage of À 4.5 V. Computational investigations indicted proper charge separation of the energy levels for the phenanthro[9,10-d] imidazole containing nitro group. Frontier molecular orbitals and the packing patterns obtained from computational studies suggest an efficient band gap for better device operation. The ordered morphologies of the molecules obtained from SEM analysis prove to be beneficial in the OFET performance. The photophysical, electrochemical and thermal properties of the molecules are studied in detail. The research work majorly emphasized on structural designing of the phenanthro[9,10-d]imidazoles for potential applications in organic devices.
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