title: Charge transport in light emitting devices based on colloidal quantum dots and a solution-processed nickel oxide layer.
abstract: We fabricated hybrid light emitting devices based on colloidal CdSe/ZnS core/shell quantum dots and a solution-processed NiO layer. The use of a sol-gel NiO layer as a hole injection layer (HIL) resulted in overall improvement in device operation compared to a control device with a more conventional poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) HIL. In particular, luminous efficiency increased substantially because of the suppression of excessive currents and became as large as 2.45 cd/A. To manifest the origin of current reduction, temperature- and electric field-dependent variations of currents with respect to bias voltages were investigated. In a low bias voltage range below the threshold for luminance turn-on, the Poole-Frenkel (PF) emission mechanism was responsible for the current-density variation. However, the space-charge-limited current modified with PF-type mobility ruled the current-density variation in high bias voltage range above the threshold.
authors.affiliation: Department of Energy Systems Research, Ajou University , Suwon, Gyeonggi-do 443-749, Republic of Korea.
authors.forename: Huu Tuan
authors.initials: HT
authors.lastname: Nguyen
authors.forename: Huiseong
authors.initials: H
authors.lastname: Jeong
authors.forename: Ji-Yong
authors.initials: JY
authors.lastname: Park
authors.forename: Y H
authors.initials: YH
authors.lastname: Ahn
authors.forename: Soonil
authors.initials: S
authors.lastname: Lee