Dendritic dielectric layer with urea/malonamide linkage for air stable n-channel organic thin film transistors
Date Issued
2016
Date
2016
Author(s)
Hsu, Yu-Yi
Abstract
A series of urea/malonamide dendritic molecules were prepared as gate dielectric insulator for organic thin film transistors (OTFTs). The series of molecules possess various numbers of peripheral stearyl groups with the different degrees of branching (from low to high: G0.5, G1, G1.5, G2 and G2.5). In addition, several tetracarboxylic diimides derivatives such as NDI-C4F7, NDI-C7F9, PDI-C4F7 and PDI-C7F9 with fluorinated alkyl end groups were used as semiconducting layers of OTFT due to the good stability in air. Numbers of n-channel OTFTs were fabricated by spinning the dendritic gate insulators on Si/SiO2 substrates, and then depositing the semiconducting layers in vacuum. This type of OTFTs with G1.5 as gate dielectric insulator showed the enhancement of electron mobility about 1-2 order than the device modified by octadecyltrichlorosilane (ODTS) . In particular, the device with G1.5 as insulator and PDI-C4F7 as semiconductor exhibited the best n-channel properties. The electron mobility and on/off ratio measured in the air were 3.80 cm2V-1s-1 and 7.7 x 103, respectively. Vth shift (Vide infra) The investigation of the influence on semiconducting layers was performed by atomic force microscopy (AFM) and Grazing incidence wide-angle X-ray scattering (GIWAXS). In fact, the film quality of gate insulators is dependent on the thermal properties, surface energies and generation of dendrons. Better film quality would favor the ordered arrangement of semiconducting molecules, hence the properties of gate insulator such as contact angle, dielectric constant and thermal stabilities were also studied in this work.
Subjects
dendritic urea/malonamide
gate dielectric insulator
organic thin film transistors (OTFTs)
Type
thesis
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