The Formation of Exciplex and Improved Turn-on Voltage in a Hybrid Organic-Inorganic Light-Emitting Diode

In order to take advantage of organic and inorganic materials, we chose the polymer MEH-PPV as the luminous layer and ZnS as the electron transporting layer to prepare hybrid organic-inorganic light-emitting diodes (HOILEDs): ITO/MEH-PPV(～70 nm)/ZnS(20 nm)/Al by thermal evaporation and spin coating. Compared with the single-layer device ITO/MEH-PPV(～70 nm)/Al, spectral broadening and a slightly red shift are observed. Compared with the pure organic device ITO/MEH-PPV(～70 nm)/BCP (20 nm)/Al and combined with the energy level structure diagram, it is concluded that the spectral broadening and red shift are due to the exciplex luminescence at the interface between MEH-PPV and ZnS or BCP. In addition, the hybrid inorganic-organic device shows a lower turn-on voltage, but the current efficiency is lower than that of the pure organic device with the same structure.