Experimental analysis of dark frame growth mechanism in organic light-emitting diodes

Abstract

Organic light-emitting diodes (OLEDs) were fabricated with heterojunction interfaces and layers that were prepared by cold isostatic pressing (CIP), and the growth characteristics of their non-emission areas, or dark frames (D/Fs), were investigated during storage. We fabricated an OLED with an indium-tin-oxide (ITO)/N,N $-di(1-naphthyl)-N,N $-diphenyl-(1,1$-biphenyl)-4,4$-diamine (α-NPD)/tris(8-hydroxylquinoline)aluminum (Alq 3 )/ LiF/Al structure without CIP treatment (Device I), as well as OLEDs that were pressed after the deposition of α-NPD (Device II), Alq 3 (Device III), and LiF/Al (Device IV) layers. Although Devices I, II, and III showed typical D/F growth characteristics, the D/F growth rate in Device IV was markedly mitigated, indicating that the Alq 3 /LiF/Al interfaces dominated the D/F growth. Moreover, we found that the electron injection characteristic was poorer in the electron-only device stored after the LiF layer deposition than in that stored before the LiF deposition. Therefore, the decreased electron injection due to storage at the interfaces was attributed to the D/F growth.

Penetration of a Mg:Ag alloy electrode thermal deposited on an organic thin film

“…[1][2][3] The organic/metal interfaces are generally formed by thermal evaporation of the metal electrode on to the organic under-layers. [4][5][6] In the case of a polycrystalline organic under-layer, metal electrode deposition causes migration of metal particles to the underlayer along with grain boundaries. 7) On the other hand, many organic devices, e.g.…”