Abstract
Abstract
Phenanthroimidazole derivative with Pyrene (PhenI-Py), which is known to be a good blue emitter, has been used to make OLED devices. We report the tuning of the emission from green (peak emission at 535 nm) to cyan (peak emission at 495 nm) in OLEDs by changing the device geometry using different hole transporting layers (HTL). Cyan OLEDs reported a high external quantum efficiency (EQE) of ∼10%. By making devices with different thicknesses of the active layer and hole transporting layers (HTL), this wavelength shift could be understood on the basis of the shift in the recombination zone (RZ). Time resolved area normalized emission spectroscopy (TRANES) carried out in thin films of PhenI-Py indicated the dynamics of excited states, which seem to be responsible for the observed RZ shift. Thus, our results present an understanding of the mechanism of the observed colour tunability in devices of PhenI-Py.