Abstract
We demonstrated modulation of charge carrier densities in all-solution-processed organic field-effect transistors (OFETs) by modifying the injection properties with self-assembled monolayers (SAMs). The all-solution-processed OFETs based on an n-type polymer with inkjet-printed Ag electrodes were fabricated as a test platform, and the injection properties were modified by the SAMs. Two types of SAMs with different dipole direction, thiophenol (TP) and pentafluorobenzene thiol (PFBT) were employed, modifying the work function of the inkjet-printed Ag (4.9 eV) to 4.66 eV and 5.24 eV with TP and PFBT treatments, respectively. The charge carrier densities were controlled by the SAM treatment in both dominant and non-dominant carrier-channel regimes. This work demonstrates that control of the charge carrier densities can be efficiently achieved by modifying the injection property with SAM treatment; thus, this approach can achieve polarity conversion of the OFETs.
Highlights
Non-negligible, the ambipolar characteristics of the organic field-effect transistors (OFETs) begin to appear
We focused on controlling the charge carrier densities by modification of the injection property in OFETs because of two particular advantages: compatibility with a wide range of systems and suitability for studies of the intrinsic nature of charge transport in organic semiconductors
The injection barrier was controlled using two types of self-assembled monolayer (SAM), TP and pentafluorobenzene thiol (PFBT), and the modified work function of the inkjet-printed Ag electrodes was confirmed by ultraviolet photoelectron spectroscopy (UPS) measurements
Summary
Non-negligible, the ambipolar characteristics of the OFETs begin to appear. if the density of the non-dominant carriers surpasses the density of the dominant carriers, the OFETs return to the unipolar state but with reversed polarity. The injected carrier density can be modulated through tuning of the injection property[22,23,24] Among these methods, we focused on controlling the charge carrier densities by modification of the injection property in OFETs because of two particular advantages: compatibility with a wide range of systems and suitability for studies of the intrinsic nature of charge transport in organic semiconductors. The second described method, interface engineering at the organic semiconductor–gate insulator interface, exhibits a drawback in terms of universality In this method, the charge carrier densities are controlled via an induced dipole from the interfacial layer between, for example, a self-assembled monolayer (SAM) and a high-permittivity polymer. We investigated the density modulation of the non-dominant carriers (i.e., holes) by employing the SAMs in the all-solution-processed n-type OFET
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