Pure exciplex-based white organic light-emitting diodes with imitation daylight emissions

Abstract

An exciplex could be formed by blending a selected hole-transporting material (HTM)/electron-transporting material (ETM) pair, and the corresponding energy band gap is roughly determined by the energy difference between the lowest unoccupied molecular orbital (LUMO) of the ETM and the highest occupied molecular orbital (HOMO) of the HTM. In this study, three HTM/ETM combinations are adopted to generate blue, green, and red exciplexes, allowing us to design precise device architectures for the fabrication of exciplex-based white OLEDs (WOLEDs) with daylight-like emissions. The CIE coordinates of this WOLED varied close to the Planckian locus as the biases increase, with a high color rendering index of about 96. This high performance suggests this exciplex-based WOLED can provide high-quality white-light illumination. Photoluminance and lifetime measurements of the exciplex behavior of the HTM/ETM combinations indicate that the HTM and ETM selected should possess higher triplet energy bandgaps than those of their corresponding exciplex to avoid energy loss.