Fully Additive Low-Cost Printed Electronics With Very Low Process Variations

Low-cost printed electronics (PE) on flexible substrates necessitates that its printing process embodies only additive steps (vis-à-vis subtractive steps), and processing at low temperature (e.g., <;120 °C) and in an air-only environment. For the manufacturability of PE circuits and systems, it is imperative that the printing process features low process variations, where the primary parameter is carrier mobility μ; and in some cases, the primary parameter is threshold voltage V
_th
. We present a novel screen-printing low-cost fully additive all-air-processed low-temperature PE printing process featuring very low process variations. In particular, the process variations are ±4.9% μ and ±0.43 V V
_th
. To the best of our knowledge, this is the smallest μ variations amongst all reported fully additive printing processes, and comparable to the best of subtractive processes. These very low variations are achieved by blade coating the semiconductor layer comprising a polymer-small molecular blend in a dual-solvent system, yielding a precise control of the semiconductor film formation. Further by means of careful layout, the matching between our two printed organic thin-film transistors is markedly improved from 7.2% (arising from ±4.9% μ and ±0.43 V V
_th
variations) to 2.1%-to date, the best reported matching.