Influence of Exciplex formation on the electroluminescent properties of dimeric Zn (II) bis‐2‐(2'‐hydroxyphenyl) benzoxazole complex and monomeric Zn (II) 2‐(1'‐hydroxynaphthyl) benzothiazole complex

摘要

In this paper we present the factors affecting electroluminescent properties of Zinc complexes of oxazole & thiazole derivatives. Electroluminescent spectra of the Zinc (II) complex of bis‐[2‐(2'‐hydroxyphenyl) benzoxazole], [Zn(HPBO)_2]_2 and 2‐(1'‐hydroxynaphthyl) benzothiazole [Zn(HNBT)_2] show unusual broadening and shows structural and photophysical similarity with [Zn(HPBT)_2]_2, a dimeric complex. The [Zn(HPBO)_2]_2 complex as an emissive layer in the device structure ITO ∕PEDOT:PSS ∕TPD (30nm) ∕[Zn(HPBO)_2]_2 (60nm) ∕BCP (6nm) ∕Ca (3nm) ∕Al (200nm) shows a broad bluish green emission, with a full width at half maxima (FWHM1～70nm). The EL spectra is much broader compared to the PL spectra because of exciplex formation at the interfacial region between the emissive layer (EML) & hole transport layer (HTL). We also show the device performance of Zinc 2‐(1'‐hydroxynaphthyl) benzothiazole [Zn (HNBT)_2] complex as emissive layer. Distinctly this device shows a broad greenish yellow emission with a peak maxima at 535nm and 690nm, owing to the exciplex formation between electron transport layer (ETL) and emissive layer (EML), which is in sharp contrast to the exciplex formation across the HTL‐EML interface observed for the [Zn(HPBO)_2]_2 complex.