Highly Efficient Mixed Conduction in N-type Fused Small Molecule Semiconductors

Highly efficient mixed ionic and electronic conduction is critical to developing high-performance organic electrochemical transistors (OECTs) devices. While currently, the n-type small molecules mixed conductors design strategy remains extremely lacking. Herein, ethylene glycol (EG) chain substituted electron-deficient naphthalene bis-isatin and rhodanine acceptor units with easily accessible steps are rationally fused, affording fused and planar novel semiconductors with weak intramolecular S-O 'conformation locks', where gNR with EG side chain and hgNR with hybrid alkyl-EG side chain. The rigid, planar and highly electron-deficient skeleton enables the resulting small molecule semiconductors to be efficient mixed ionic-electronic conductors with very high OECT electron mobility up to 0.01 cm(2) V-1 s(-1). Remarkedly, gNR displays the record value of geometry-normalized transconductance of 0.4 S cm(-1) and mu C* of 2.6 F V-1 cm(-1) s(-1), which can also be compared with the state-of-art n-type semiconducting polymers in OECTs. Moreover, the effect of the alkyl spacer on the n-type mixed ionic and electronic conduction features of the small molecule materials is investigated. The fused electron-deficient acceptor-acceptor (A-A) system with intramolecular conformation lock design strategy in this work provides a new avenue to realize next-generation high-performance small molecule mixed ionic and electronic conductors for OECT materials.

Automated summary

This study presents a design strategy for n-type small molecule mixed conductors by combining electron-deficient naphthalene bis-isatin and rhodanine acceptor units substituted with ethylene glycol (EG) chains. The resulting fused and planar semiconductors exhibit efficient mixed ionic-electronic conductors with high OECT electron mobility. The study also investigates the effect of the alkyl spacer on the conduction features of the small molecule materials. This work provides a new avenue for the development of high-performance small molecule mixed ionic and electronic conductors for OECT materials.