Suitability of lithium doped electron injection layers for organic semiconductor lasers

Lithium doped 2 , 2 ′ , 2 ″ -(1,3,5-benzenetryl)tris(1-phenyl)- 1 H -benzimidazol (TPBi) as electron injection layer in organic laser diodes is investigated. The optical material absorption of optimum doped Li:TPBi is as low as 300 cm − 1 at λ = 600 nm . Kelvin probe analysis demonstrates that thin layers ( 5 nm ) of Li:TPBi already enable efficient electron injection from low optical loss transparent conducting oxide contacts. Moreover, stable current densities of about 100 A ∕ cm 2 can be injected. The waveguide losses added due to these Li:TPBi layers can be as low as 3 cm − 1 . These results present a major step towards electrically contacted, low-loss organic laser structures.