title: Combining an ionic transition metal complex with a conjugated polymer for wide-range voltage-controlled light-emission color.
abstract: We report on voltage-controlled electroluminescence (EL) over a broad range of colors from a "two-luminophor" (2L) light-emitting electrochemical cell (LEC), comprising a blend of a majority blue-emitting conjugated polymer (blue-CP), a minority red-emitting ionic transition metal complex (red-iTMC), and an ion-transporting compound as the active layer. The EL color is reversibly shifted from red, over orange, pink, and white, to blue by simply changing the applied voltage from 3 to 7 V. An analysis of our results suggests that the low concentration of immobile cations intrinsic to this particular device configuration controls the electron injection and thereby the EL color: at low voltage, electrons are selectively injected into the low-barrier minority red-iTMC, but with increasing voltage the injection into the high-barrier majority blue-CP is gradually improved.
authors.affiliation: The Organic Photonics and Electronics Group, Umeå University , SE-901 87 Umeå, Sweden.
authors.forename: Jia
authors.initials: J
authors.lastname: Wang
authors.forename: Shi
authors.initials: S
authors.lastname: Tang
authors.forename: Andreas
authors.initials: A
authors.lastname: Sandström
authors.forename: Ludvig
authors.initials: L
authors.lastname: Edman
keywords: charge injection; conjugated polymer; ionic transition metal complex; light-emitting electrochemical cell; tunable color; white emission