Water permeation pathways in laminated organic single-crystal devices

TL;DR

This study investigates water permeation pathways in organic single-crystal transistors, revealing that the interface between the crystal and substrate is the main pathway for water ingress, which affects device stability.

Contribution

It demonstrates that water does not penetrate the crystal itself but mainly permeates at the SC/substrate interface, emphasizing the importance of conformal lamination.

Findings

Water-induced instabilities increase with crystal thickness.

Molecular dynamics show no water penetration into the crystal.

Interface at SC/substrate is the dominant permeation pathway.

Abstract

Water permeation pathways in electronic devices should be eliminated for the suppression of operational instabilities. We investigated possible pathways in field-effect transistors based on a laminated single crystal (SC) of an organic semiconductor, rubrene. Water-induced instabilities were found to be more obvious with a thicker rubrene SC. Furthermore, under our simulation conditions, molecular dynamics calculations of water diffusion on a rubrene SC showed that no water molecules penetrated the SC. These findings indicate that a space at the SC/substrate interface is a dominant pathway. The present study clearly shows the importance of conformality of SC lamination onto the underlying substrate.