Direct evidence of n-type doping in organic light-emitting devices: N free Cs doping from CsN3

摘要

Cesium azide (CsN3) is confirmed to be decomposed during thermal evaporation. Only Cs could be deposited on tris(8-hydroxyquinolinato)aluminum (Alq3) and n-type doping is easily achieved. Organic light-emitting devices with CsN3 show highly improved current density-luminance-voltage characteristics compared to the control device without CsN3. To understand the origin of the improvements, in situ x-ray and UV photoemission spectroscopy measurements were carried out and a remarkable reduction in electron injection barrier is verified with successive deposition of Al on CsN3 on Alq3. CsN3 has a potential as alternative to doping the electron transport layer by replacing the direct deposition of alkali metals.