Abstract
In recent years organic field-effect transistors have received extensive attention, however, it is still a great challenge to fabricate monolayer-based devices of conjugated polymers. In this study, one single layer of poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene) is directly dip-coated, and its self-assembly is precisely tuned from nanofibers to granular aggregates by controlling the dielectric roughness on a sub-nanometer scale. The charge carrier transport of the monolayer transistor exhibits a strong dependence on the dielectric roughness, which is attributed to the roughness-induced effects of higher densities of grain boundaries and charge trapping sites as well as surface scattering. These results mark a great advance in the bottom-up fabrication of organic electronics.
Highlights
In the past two decades, tremendous progress has been made in both organic semiconducting materials and device engineering for organic field-effect transistors (OFETs)
It has been widely proven and accepted that the first few layers near the dielectric are primarily responsible for the charge carrier transport in OFETs.[1]
A monolayer of 1,4bis((5′-hexyl-2,2′-bithiophen-5-yl)ethynyl)benzene was grown in the formation of two dimensional single crystals by dropcasting, and an excellent charge carrier transport was reported with the mobility up to 1 cm[2] V−1 s−1.6 Such monolayer transistors could bear great potential in the near future due to their unique advantages such as lower cost, higher sensitivity and transparency.[7]
Summary
In the past two decades, tremendous progress has been made in both organic semiconducting materials and device engineering for organic field-effect transistors (OFETs). We proposed an effective solution method to precisely tune the Rms value of the SiO2 surface on a sub-nanometer scale by which the intrinsic role of the interfacial order of organic semiconductors on the charge carrier transport was successfully revealed.[16] In the present study, a donor–acceptor copolymer, poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1b:3,4-b′]-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT, Fig. 1), is processed into a monolayer by dip-coating which is a known technique to deposit organic semiconductors in a welldefined manner.[17,18,19] Dielectrics with sub-nanometer roughness (S1–S4) are employed to kinetically control the self-assembly of this conjugated polymer monolayer.
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