Abstract

Samarium (dibenzoylmethanato)3 bathophenanthroline (Sm(DBM)3 bath) was employed as an emitting and electron transport layer in organic light emitting diodes (OLEDs), and narrow electroluminescent (EL) emissions of a Sm3+ ion were observed in the visible and near infrared (NIR) region, differing from those of the same devices with Eu3+- or Tb3+-complex EL devices with the same structure. The EL emissions of the Sm3+-devices originate from transitions from 4G5/2 to the lower respective levels of Sm3+ ions. A maximum luminance of 490 cd m−2 at 15 V and an EL efficiency of 0.6% at 0.17 mA cm−2 were obtained in the visible region, and the improved efficiency should be attributed to introducing a transitional layer between the N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-diphenyl-4,4′-diamine (TPD) film and the Sm(DBM)3 bath film and the avoidance of interfacial exciplex emission in devices. Sharp emissions of Sm3+ ions in the NIR region were also observed under a lower threshold value less than 4.5 V.

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