Thin-film encapsulation of top-emission organic light-emitting devices with polyurea/Al2O3 hybrid multi-layers

We developed a room-temperature encapsulation process based on multi-stack of ultra thin Al₂O₃ and polyurea layers for top-emission organic light-emitting devices (TEOLEDs). Device structure, including a capping layer for refractive-index matching and a thick polyurea buffer layer, was optimized to enhance light extraction without distorting electroluminescence spectrum. The efficiency of a TEOLED encapsulated with 5 pairs of Al₂O₃(50 nm)/polyurea(20 nm) layers was better than that of a glass-encapsulated TEOLED, whereas their color coordinates were almost identical. Moreover, the half-decay lifetime of a TEOLED encapsulated with 5 pairs of Al₂O₃/polyurea layers was 86% of that of a glass-encapsulated TEOLED. Water vapor transition rate of 5 pairs of Al₂O₃(50 nm)/polyurea(20 nm) layers on PET film was measured as low as 5 × 10⁻⁴ g/m² day.