Exciplex emission and its relationship with depletion organic heterojunction

Exciplex emission is a special form of luminescence from excited state complex formed between two contacting materials at interface in organic light-emitting devices (OLEDs). While considerable works has been focused on the role of exciplex states in interfacial light emitting processes, the understanding for the fundamental forming criteria of exciplex states is limited. In this work, six pairs of exciplex-forming organic materials were examined using photoemission spectroscopies. Interestingly, all the studied pairs show special charge transfer with N-type material donates a considerable amount of electron to the contacting P-type material, leading to energy levels bending and depletion of mobile majority carriers on the two sides of the junction, i.e. Pδ−–Nδ+. The close relation between the depletion organic HJs and the exciplex emission is discussed.

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► Six pairs of exciplex-forming organic materials were examined.
► All exciplex-forming pairs show depletion of mobile carriers at the junctions.
► The relation between the depletion organic HJs and exciplex emission is discussed.