Self-assembled monolayers in organic electronics

PhD ceremony: Ms. F. Gholamrezaie, 16.15 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Self-assembled monolayers in organic electronics

Promotor(s): prof. D.M. de Leeuw, prof. P.W.M. Blom

Faculty: Mathematics and Natural Sciences

In recent years organic semiconductors have attracted considerable attention for application in electronic devices such as solar cells, light-emitting diodes and field-effect transistors. The advantages of the use of polymers are their unique electrical and mechanical properties and the opportunity to produce low-cost electronics on large area substrate such as glass and plastic.

A promising technology for organic electronics is bottom-up self-assembled monolayer (SAM), where molecules self-organize into complex patterns and structures without human intervention. Despite being only a single molecular layer thick, the SAM can change the macroscopic mechanical and electrical properties of surfaces. SAMs are applied onto the metal electrodes to tune the work function. The charge injection into the semiconductor can be enhanced or suppressed. Controlling the threshold voltage in OFETs can be done by SAMs. SAMs made from conjugated molecules can act as semiconducting layers in an OFET, it is shown that monolayer OFETs can surprisingly be made by simple spin coating. The mobility of the semiconductor is comparable with that of a bulk layer of the same material. The SAMFETs can also made by solution process. The SAMFETs made with SiO2 as the gate dielectric cannot be used for flexible electronics as the substrate is not bendable. The fully functional circuits demonstrate long-range order over large areas of a bare polymer surface, which can be regarded as the start of flexible monolayer electronics is the main report of this thesis.