Light exposure dependence of field-effect mobility of pentacene thin films deposited on very thin polyimide photo-alignment layers

Abstract

We report the anisotropic field-effect hole mobility of 30 nm-thick pentacene films deposited on 1.6 nm-thick polyimide photo-alignment layers with different in-plane anisotropy. To induce different in-plane anisotropy, the light exposure was varied up to 16 J/cm2. In this light exposure range, the long molecular axis of pentacene was standing with respect to the substrate surface (c*-axis oriented “thin film phase”), and the pentacene molecular plane was oriented on average parallel to the average alignment direction of the underlying polyimide backbone structures. For light exposures of 6 and 11 J/cm2, the field-effect mobility for the current flow direction parallel (perpendicular) to the alignment direction of pentacene molecular plane was enhanced (suppressed) compared to that of the pentacene film deposited on non-aligned polyimide film. This field-effect mobility enhancement shows a positive effect of the in-plane alignment control of pentacene molecules. However, the field-effect mobility decreased at a light exposure of 16 J/cm2, even though the in-plane orientation order of the pentacene molecular plane slightly increased. The causes for the mobility enhancement at 6 and 11 J/cm2 and the mobility decrease at 16 J/cm2 were discussed.

Liquid crystal templating as an approach to spatially and temporally organise soft matter

“…As expected, examples of patterned non-LC materials are still sparse; only pentacene was successfully aligned using this approach. [154][155][156] Recently, our group applied this command layer approach to spatially pattern self-assembling amphiphilic materials in aqueous LCLC environments in domains of several tens of micrometres. After photopolymerization, these assemblies are transformed in optically active p-conjugated polydiacetylenes.…”

Introducing a Surface-Enhanced-Raman-Scattering Enhancer for Experimental Estimation of the Debye Screening Length in Organic Field-Effect Transistors

“…In the past decades, organic field-effect transistors (OFETs) have attracted considerable attention because of their potential applications in low-cost flexible electronic sensors and detectors. − The special device physics mainly come from the additional gate besides drain and source electrodes . The gate voltage by the field effect would induce a dramatic change of electric potential both along and perpendicular to the channel, which is the basic of high mobility and stable output.…”