title: Trifluoromethylation of tetraphenylborate counterions in cationic iridium(III) complexes: enhanced electrochemical stabilities, charge-transport abilities, and device performance.
abstract: Trifluoromethylation of tetraphenlyborate counterions was successfully used to improve the electrochemical stabilities and device performance of cationic iridium(III) complexes. Melioration of the thermal, photoluminescent, electrochemical, and electrophosphorescent characteristics was achieved. Interionic hydrogen bonds were first found between the aromatic hydrogen atoms in the ancillary ligands of cations and the fluorine atoms in the trifluoromethyl groups of the anions. The strong impact of the counterions on the charge transport in the devices was investigated. A compound with two trifluoromethyl groups in the tetraphenlyborate ion shows the highest photoluminescent efficiency, the best electrochemical stability, and the greatest performance in green-blue-emitting devices, with a high current efficiency of 12.4 cd A(-1) and an emission peak at λ=480 nm. The efficiencies achieved are the highest reported for OLEDs with ionic complexes emitting in the blue-green region.
authors.affiliation: Key Lab of Organic Optoelectronics and Molecular Engineering of the Ministry of Education, 100084 (P.R. China).
authors.forename: Dongxin
authors.initials: D
authors.lastname: Ma
authors.forename: Lian
authors.initials: L
authors.lastname: Duan
authors.forename: Yongge
authors.initials: Y
authors.lastname: Wei
authors.forename: Yong
authors.initials: Y
authors.lastname: Qiu
keywords: complex chemistry; hydrogen bonds; iridium; organic light-emitting diodes; tetraphenylborates