Electronic properties of porphyrin-based organic transistors.

Abstract

Organic thin-film field-effect transistors (OFETs) using metallotetrabenzoporphyrins (MTBPs) as the active material are of particular interest in organic electronics because free-base TBP OFETs have demonstrated high degrees of electrical performance, and the TBP molecule itself is easily altered, opening paths to customizing the active material of the OFET to the application. Metalloporphyrins are the foundation for several vital biological systems, including chlorophyll and hemoglobin. Thus, exploring the electronic properties of organic semiconductors developed from derivatives of such molecules is worthwhile in that electronic devices fabricated from such materials will likely be biocompatible. This dissertation begins by succinctly surveying the developments in OFET technology relevant to solution-processable small molecule organic semiconductors. The electronic and crystallographic properties of solution-processed TBP are then examined. Following discussion on characteristics of free-base TBP, OFETs fabricated using Cu and Ni core substitutions of TBP are examined. Variation in OFET performance is discussed with respect to the morphological properties of their thin-films. The experimentally examined materials are then examined using solid-state <italic>ab initio</italic> calculations based on density functional theory to determine changes to their electronic bandstructures. The opportunity is also taken to examine several MTBP-based molecules not yet synthesized, so as to determine what core substitutions might make the best OFETs. The effects of trap formation are also examined using the <italic> ab initio</italic> calculations. Finally, the properties of MTBP thin-films on organic gate dielectrics are examined, and OFETs on flexible substrates developed.