Search

The transport properties of 3,10-ditetradecylpicene ((C14H29)2-picene) and [6]phenacene thin-film field-effect transistors (FETs) on Si and plastic substrates are reported, in which SiO2 and parylene are used as gate dielectrics, respectively. These devices show p-channel normally-off FET characteristics. A μ value of 1.34 cm2 V−1 s−1 is obtained in the (C14H29)2-picene thin-film FET, where 500 μm thick polyethylene terephthalate (PET) and 1 μm thick parylene are used as the substrate and gate dielectric, respectively. Moreover, excellent FET performance is obtained in the (C14H29)2-picene thin-film FET using a high-k gate dielectric, ZrO2, which is formed on a 350 μm thick PET substrate, showing p-channel normally-off FET properties and low voltage operation. The μ value reaches 6.31 cm2 V−1 s−1 in the FET device. The FET properties of N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDIC8) thin-film FETs formed on PET are also reported, showing n-channel normally-off FET characteristics. We report a bias stress effect on flexible [6]phenacene thin film FETs that are fabricated on a PEN substrate. Two types of experiments are performed for investigating the bias stress effect on FETs, and the bias stress effect under light irradiation is very different from that under no irradiation. This difference is well explained based on the hole-filling of trap states by electron excitation. We show the characteristics of a complementary MOS inverter (CMOS), constituting a [6]phenecene thin-film FET (p-channel) and a PTCDIC8 thin-film FET (n-channel) formed on the PET and PEN substrates, i.e., a flexible CMOS inverter. The maximum gain reaches 300. Furthermore, we report low-voltage operation for the flexible CMOS inverter, where ZrO2 is used as the gate dielectric. Through this study, we have achieved the fabrication of flexible thin-film FETs with a high μ and low voltage operation, and flexible CMOS inverters with a high gain as well as low operation voltage. This study could provide a basis for future practical/human-compatible electronic devices.

The synthesis of a hexacyclic fused polyheteroaromatic system, namely carbazolo[2,1-a]carbazole, via a simple two-step route is reported. Additionally, the characterization of its electronic structure is described, corresponding to a very stable molecule that is also transparent to visible light. Solid state packing is determined by X-ray diffraction analysis which, in combination with the computational calculation of the charge transfer parameters, reveals an adequate molecular arrangement to achieve a low anisotropic environment for charge transport. This π-conjugated system is used as an organic semiconductor for the fabrication of thin film and single crystal organic field-effect transistors (OFETs). Furthermore, the evaluation of different gate dielectrics results in transistors with very good hole mobilities and low operating voltages. In agreement with these results, carbazolo[2,1-a]carbazole becomes one of the best organic semiconductors belonging to the family of carbazole-based azaphenacenes.

Field-effect transistors (FETs) have been fabricated with thin films of a series of 2,9-dialkylated phenanthro[1,2-b:8,7-b′]dithiophene derivatives (Cn-PDTs). The FET characteristics of Cn-PDT thin-film FETs with an SiO2 gate dielectric as well as high-k gate dielectrics were recorded, and the dependence of the field-effect mobility, μ, on the number (n) of carbon atoms in the alkyl chains was investigated, showing that the 2,9-didodecylphenanthro[1,2-b:8,7-b′]dithiophene (C12-PDT) thin-film FET displays superior properties, with μs as high as 1.8 cm2 V−1 s−1 for the SiO2 gate dielectric and 2.2 cm2 V−1 s−1 for the HfO2 gate dielectric. The average μ values, 〈μ〉, reach 1.1(5) and 1.8(6) cm2 V−1 s−1, respectively, for the SiO2 and ZrO2 gate dielectrics. Low-voltage operation, showing an absolute average threshold voltage 〈|Vth|〉 of ∼11 V, was implemented, together with the above high 〈μ〉 of ∼2 cm2 V−1 s−1. Also, a flexible FET was fabricated with a parylene gate dielectric. The results of this study show the potential of the C12-PDT molecule for application in a high-performance transistor.

Correction for ‘Transistor application of new picene-type molecules, 2,9-dialkylated phenanthro[1,2-b:8,7-b′]dithiophenes’ by Yoshihiro Kubozono et al., J. Mater. Chem. C, 2015, 3, DOI: 10.1039/c4tc02413c.