•Two-dimensional-growth high quality TCTA thin film was fabricated by USC.•USC-TCTA film possesses more uniform surface topography.•The optical property, electrical property and formation mechanism of USC-TCTA film are studied.•The green OLEDs based on USC-TCTA film perform excellent performances.Two-dimensional-growth small molecular organic thin film with high quality is fabricated by ultrasonic spray coating technology (USC) from the toluene solution of 4,4′,4″-tris (carbazol-9-yl) triphenylamine (TCTA). In comparison to the vacuum thermal evaporation (VTE) TCTA film, the USC-TCTA film obtained from liquid-phase solution possesses more uniform surface topography. The differences between the USC-TCTA and the VTE-TCTA in optical property, electrical property and formation mechanism are also studied in detail. Besides, to evaluate the hole transport and electron blocking ability of USC-TCTA film, the organic light-emitting devices (OLEDs) employing USC-TCTA film as hole transport layer are fabricated successfully. Additionally, the green OLEDs based on USC-TCTA film perform as well as the ones with VTE-TCTA film in current density, luminance, efficiency and color stability, and show even better tolerance to high bias voltage.Download high-res image (563KB)Download full-size image

•White inverted top-emitting organic light-emitting devices were demonstrated.•Bphen:Ag interlayer was used to enhance the electron injection.•Ag–Ge–Ag capping with light outcoupling layer was used as anode.•The device shows stable spectra with voltage and viewing angle.By adopting an 4,7-diphenyl-1,10-phenanthroline (Bphen):Ag interlayer with the gradient structure between the cathode and electron injection layer, the electron injection of white inverted top-emitting organic light-emitting devices (WITOLED) was enhanced. The structure of Ag–Ge–Ag anode capping with light outcoupling was used to ensure the spectral stability with the angles. The structure of the emission layer was carefully designed to guarantee the spectral stability with the voltages. The highest current efficiency of the WITOLED can reach 21.7 cd/A. The CIE 1931 coordinates varies only 0.022 in X and 0.015 in Y (0o–60o).

By adopting a phosphorescent host/guest system consisting of blue iridium complex as host and a series of phosphorescent dyes as guest, efficient and low-voltage monochromic organic light-emitting devices(OLEDs) were fabricated. The devices with blue iridium host have higher power efficiency than the device with the conventional host 4,4′-N,N′-dicarbazole-biphenyl. The enhancement of the maximum power efficiency in green phosphorescent device can reach 37.2%. Dichromatic white OLED could be achieved by simply adjusting the concentration of the orange dyes. At a brightness of 1000 cd/m2, the power efficiency of the white device is 8.4 lm/W with a color rendering index of 76.

We present a simulation of the optical properties of ITO-free top-emitting white organic light-emitting devices (TEWOLEDs). Metals (Al, Ag, Mo, Cu, Au, Sm) are used as anode or cathode depending on their work functions. Besides, devices with 1D metallic–dielectric photonic crystal anode are also demonstrated. The influence of the capping layer or the metallic–dielectric multilayer structure on the optical properties (such as efficiency, angular emission characteristics, color gamut and color rendering index) of the devices has been investigated. The results indicated that TEWOLEDs can be used as lighting with high color rendering index or as a display with wide color gamut by carefully designing the structure of the devices.Graphical abstractHighlights► Optical properties of ITO-free top-emitting white organic light-emitting devices (TEWOLED) were simulated and optimized. ► Metal–metal microcavity TEWOLED could be used as lighting with high CRI. ► TEWOLED with 1D metallic–dielectric photonic crystal anode could realize a near-to-eye display with a wide color gamut.

A microring resonant wavelength demulti/multiplexer (MRRWDM) based on UV-written technology is designed. By using a double smooth octagon microrings structure, a 1 × 8 device around the central wavelength of 1550.918 nm with the wavelength spacing of 1.4 nm is presented. Analytical results based on coupled mode theory show that the 3 dB bandwidth is about 0.22 nm, the insertion loss is less than 0.7 dB, and the crosstalk is below −47 dB for every output channel of the designed device without tolerances.