Transparent-cathode for top-emission organic light-emitting diodes

A transparent-charge-injection layer consisting of LiF/Al/Al-doped SiO has been developed as (i) a cathode for top-emitting organic light-emitting diodes and as (ii) a buffer layer against damages induced by energetic ions generated during deposition of other functional thin films by sputtering, or plasma-enhanced chemical vapor deposition. A luminance of 1900 cd/m(2) and a current efficiency of 4 cd/A have been achieved in a simple testing device structure of indium tin oxide (ITO) N,N-'-diphenyl-N,N-'-bis(3-methylphenyl)-1,1(')-biphenyl-4,4(')-diamine (60 nm)/Alq(3) (40 nm)/LiF (0.5 nm)/Al (3 nm)/Al-doped SiO (30 nm). A minimum thickness of 30 nm of Al-doped SiO is also found to protect organic layers from ITO sputtering damage. (C) 2003 American Institute of Physics.