Carrier Charge Polarity in Mixed-Stack Charge-Transfer Crystals Containing Dithienobenzodithiophene

Kodai Iijima; Ryo Sanada; Dongho Yoo; Ryonosuke Sato; Tadashi Kawamoto; Takehiko Mori

doi:10.1021/acsami.8b00416

Carrier Charge Polarity in Mixed-Stack Charge-Transfer Crystals Containing Dithienobenzodithiophene

ACS Appl Mater Interfaces. 2018 Mar 28;10(12):10262-10269. doi: 10.1021/acsami.8b00416. Epub 2018 Mar 15.

Authors

Kodai Iijima¹, Ryo Sanada¹, Dongho Yoo¹, Ryonosuke Sato¹, Tadashi Kawamoto¹, Takehiko Mori¹

Affiliation

¹ Department of Materials Science and Engineering , Tokyo Institute of Technology , O-okayama , Meguro-ku, Tokyo 152-8552 , Japan.

PMID: 29508608
DOI: 10.1021/acsami.8b00416

Abstract

Dithieno[2,3- d;2'3'- d']benzo[1,2- b;4,5- b']dithiophene forms mixed-stack charge-transfer complexes with fluorinated tetracyanoquinodimethanes (F _nTCNQs, n = 0, 2, and 4) and dimethyldicyanoquinonediimine (DMDCNQI). The single-crystal transistors of the F _nTCNQ complexes exhibit electron transport, whereas the DMDCNQI complex shows hole transport as well. The dominance of electron transport is explained by the superexchange mechanism, where transfers corresponding to the acceptor-to-acceptor hopping ( t_e^eff) are more than 10 times larger than the donor-to-donor hopping ( t_h^eff). This is because the donor orbital next to the highest occupied molecular orbital makes a large contribution to the electron transport owing to the symmetry matching. Like this, inherently asymmetrical electron and hole transport in alternating stacks is understood by analyzing bridge orbitals other than the transport orbitals.

Keywords: ambipolar transistor; charge-transfer complex; mixed stack; organic transistors; single-crystal transistors.