Fabrication of flexible organic top-emitting devices on steel foil substrates

A flexible organic light-emitting diode (FOLED) was fabricated on a steel foil. Stainless steel foil, spin-coated polyvinyl acetate (PVA) and silicon oxide were used as a flexible substrate, an insulating planarization layer and a buffer layer, respectively. Patterned indium tin oxide (ITO) was sputter-deposited on the buffer layer to form an anode. N,N′-bis-(1-naphthl)-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) and tris(8-quinolinolato) aluminum (Alq3) were used as a hole-transporting layer and a light-emitting/electron-transporting layer, respectively. A thin samarium layer was deposited on the organic stack to serve as a semitransparent cathode. The turn-on voltage of the resulting FOLED was 3 V, and the light-emitting efficiency reached 0.56 cd/A. The FOLED was shown to bend substantially without incurring detectable degradation.