Developing homojunction exciplex for efficient multilayer solution-processed organic light emitting diodes.

[Display omitted] • Exciplex emission was achieved by a single molecular system with flexible chain. • Ho-exciplex eliminates the phase separation drawback of physical blended exciplex. • Ho-exciplex can enable the fabrication of fully-solution-processed OLEDs. Exciplex has long been recognized as a mixture of donor and acceptor components. Here, for the first time, it was demonstrated that exciplex emission can also be achieved by single pure molecule, we named it as homojunction exciplex (ho-exciplex). By using the flexible alkyl chain to link the donor and acceptor unit, the result compound not only maintain efficient exciplex emission property, but also eliminate the notorious phase separation drawback. Different from the conventional heterojunction exciplex (he-exciplex), such unique molecular concept of homojunction system will provides a bright avenue toward structure-simplified and high-stable OLEDs without sophisticated stoichiometric and physical blending process. By using such a single molecular PhTRZ-CzTPA as both emitter and host, the solution-processed device achieved a comparable electroluminescence performance with its hybrid blending he-exciplex counterpart. Importantly, the unified molecule of PhTRZ-CzTPA makes it superior solvent resistance to isopropanol, which enable the fabrication of fully-solution-processed device with all spin-coated organic layers. Therefore, the homojunction strategy will open a new avenue for exciplex design and application, not only in OLEDs, but also other semiconductor devices or sensors. [ABSTRACT FROM AUTHOR]