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.

Effects of 1,2-ethanedithiol concentration on performance improvement of quantum-dot LEDs

“…29 For the device fabrication process, a piece of ITO glass was rst thoroughly cleaned, and the ITO layer was patterned into a cathode. 30,31 Second, a ZnO-NP solution was spin-coated onto a plasma-treated ITO cathode to form an ETL. Before the deposition of subsequent QD and organic layers, the ITO-glass substrate coated with ZnO NPs was loaded into a glove box and baked at 90 C for 30 min to eliminate any residual solvents.…”

High Hall Mobility P‐type Cu2SnS3‐Ga2O3 with a High Work Function

“…Yang et al report that the external quantum efficiency (EQE) is improved, the device stability and lifetime are significantly increased by using solution‐processed WO 3 as the HIL in QLEDs. Nguyen et al report the QLEDs with solution‐processed inorganic p‐type semiconductor NiO x as the HIL, showing a current efficiency of 2.54 cd A −1 . Vu et al report the preparation of solution‐processed MoO x film instead of PEDOT:PSS as the anode interfacial buffer layer, and the MoO x film shows better transparency, and smoother surface morphology.…”

Colloidal metal oxide nanocrystals as charge transporting layers for solution-processed light-emitting diodes and solar cells

“…Currently p-type oxides, such as NiO, or n-type oxides with high work functions, such as WO x and MoO 3 , are used to replace PEDOT:PSS, one component of the multi-layer polymeric HTLs. [186][187][188][189][190] However, the direct contact of QDs with these oxides causes severe quenching of the QD emission. More detailed studies are necessary to guide the control of interfacial interactions between the QDs and the oxide HTLs.…”