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High contrast ratio and high power efficiency organic light-emitting diodes (OLEDs) using a dual electron transporting layer of copper phthalocyanine (CuPc)/ titanium oxide phthalocyanine (TiOPc) as an anti-reflection layer have been investigated. The OLED configuration comprises indium tin oxide (ITO)/4,4′,4″-tris{N,-(3-methylphenyl)-N-phenylamino}- triphenylamine) (m-MTDATA)/N, N′-diphenyl-N,N′-bis(l-naphthyl-phenyl)-(l,l′-biphenyl)-4, 4′-diamine (NPB)/tris(8-hydroxyquinolino)-aluminium (Alq3)/CuPc/TiOPc/LiF/Al. The contrast ratio of the device with a CuPc/TiOPc anti-reflection layer is about double and the power efficiency higher than that of a conventional device without the anti-reflection layer. The improvement in the power efficiency and the contrast ratio of the device that is obtained using a CuPc/TiOPc anti-reflection layer is attributable to the stepwise electron transporting barrier and the reduced optical reflection from the cathode. The contrast ratio suffices for outdoor display applications.

In this work, we study the electrical and optical properties of organic light-emitting diodes (OLEDs) with a lithium (Li)-doped tris(8-hydroxyquinolino)-aluminum (Alq 3 ) electron transport layer (ETL). When the Li : Alq 3 doping ratio in a Li-doped Alq 3 ETL is 2 : 1, the luminous efficiency of OLEDs is 5.25 cd/A; that of an OLED without a Li-doped Alq 3 ETL is only 0.7 cd/A. X-ray photoelectron (XPS) and UV-vis absorption spectra of Li-doped Alq 3 films reveal that the Li-doped Alq 3 ETL has an improved electron conductivity. However, heavy Li doping in a Li-doped Alq 3 ETL reduces the optoelectric performance of OLEDs. Excess Li atoms or cations quench light-emitting excitons in an Alq 3 emitting layer (EML). Additionally, annealing improves the morphological stability of Li-doped Alq 3 films. An OLED, comprising a Li-doped Alq 3 ETL, requires no extrinsic thin LiF film, meeting commercial requirements, improving reproducibility and ensuring uniformality in a large area.

In the article, we describe the etching mechanism of indium-tin oxide (ITO) film, which was wet-etched using a solution of hydrochloric acid (HCl) and ferric chloride (FeCl 3 ). The etching mechanism is analyzed at various etching durations of ITO films by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and selective area diffraction (SAD) analysis. In comparison with the crystalline phase of SnO 2 , the In 2 O 3 phase can be more easily transformed to In 3+ and can form an inverted conical structure during the etching process. By adjusting the etching duration, the residual ITO is completely removed to show a designed pattern. This is attributed to the negative Gibbs energy of In 2 O 3 transformed to In 3+ . The result also corresponds to the finding of energy-dispersive X-ray spectroscopy (EDS) analysis that the Sn/In ratio increases with increasing etching duration.

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