Broadband White Electroluminescence from a Dopant-free OLED Comprising Pure Electromer and Electroplex Emission

The utilization of multiple charge transfer (CT) complex-based emissions from a bilayer organic device is a low-cost and simple technique to realize white organic light emitting diodes (WOLEDs). In this work, a WOLED structure is presented where a planar heterojunction of 1, 1-bis ((di-4-tolylamino) phenyl) cyclohexane (TAPC) / Bis [2-(diphenylphosphino) phenyl] ether oxide (DPEPO) is employed for white-lightgeneration and thereby eliminating the blend of host and dopants which is typically used as the emissive layer in OLEDs. The WOLED exhibits a broadband emission with a full-width half maxima (FWHM) of 330 nm. A systematic investigation is carried out to interpret the origins of the red (R), yellow (Y), and blue (B) components of the spectrum. It is shown that the electroplex emission originating from TAPC/DPEPO hetero-interface is responsible for the blue emission peak at a wavelength of 488 nm. The electromer emissions from TAPC and DPEPO result in yellow and red emissions with peak intensities at wavelengths 575 nm and 670 nm, respectively. By tuning the relative intensities of the RYB components, the colour of the emitted light from the OLED can be varied and a pure white emission with the CIE coordinate of (0.34, 0.36) and colour rendering index (CRI) of 89 is demonstrated.