The role of TiO2 in the air-stable hybrid organic–inorganic light-emitting diodes

The role of the TiO2 layer in hybrid organic–inorganic light-emitting diodes (HOILEDs) was discussed. A TiO2 layer was fabricated using a process that formed an “oxygen-rich” and “porous” TiO2 layer in an HOILED. The importance of the surface state on the TiO2 and the hole injection scheme in the HOILED was confirmed. All the data support the idea that HOILEDs are strongly hole-dominated LEDs, and that the TiO2 in HOILEDs plays a supporting role. The TiO2 seems to act as a hole-blocking layer.