Sr 3ar

OLEDs were fabricated on glass substrates coated with a patterned transparent ITO conductive layer. The substrates were treated with 300 W oxygen plasma. The pressure during the vacuum evaporation was 5.0 × 10⁻⁴ Pa, and the film thickness was controlled using a calibrated quartz crystal microbalance during deposition. After all layers were deposited, the OLED test modules were encapsulated with a capping glass in an evaporation chamber filled with nitrogen. The OLED characteristics of all fabricated devices were evaluated at 298 K in an air atmosphere using a voltage–current–luminance measuring system, comprising a source meter (Keithley 2400) and a spectral radiance meter (Topcon SR-3AR). The EQE was calculated using the EL spectrum, assuming that the light-emitting surface was a perfect diffusion surface; all radiance elements from every angle were added up and inputted into the formula to obtain the EQE.

The current density-voltage-luminance (J–V–L) characteristics and EL spectra were measured using a sourcemeter (2635B, Keithley) and a spectroradiometer (SR-3AR, TOPCON). EQE were calculated based on the characteristics of J–V–L and the EL spectra assumed to be Lambertian surface.

The operational lifetime, driving voltage, luminance, and electroluminescent spectra of the encapsulated OLED devices were recorded and measured using a luminance meter (SR-3AR, TOPCON, Japan) under a constant current density with an initial luminance of 1000 cd m⁻².

Pre‐patterned 50‐nm‐thick ITO‐glass substrates were treated with a wet‐cleaning process (acetone, isopropyl alcohol, and deionized water), followed by a dry‐cleaning process (UV‐ozone treatment). The organic layers were consecutively deposited on ITO‐glass substrates in thermal evaporator chambers at the rate of 0.03 to 1 Å s⁻¹ under high vacuum (<1.0 × 10⁻⁶ torr) (note that the emissive layer was co‐deposited at the rate of 0.001 to 0.5 Å s⁻¹). 150‐nm‐thick Al electrodes were thermally evaporated at the rate of 1.5 Å s⁻¹ via shadow masks. The device area was 4 mm², defined by an overlap between the anode and cathode electrodes. All devices were encapsulated in a nitrogen‐filled glovebox using UV‐curable resin with glass capsule lids prior to device characterization. The current density–voltage–luminance (J–V–L) characteristics were measured using a source meter (2636B, Keithley) and radiospectrometer (SR‐3AR, Topcon). The device lifetime was recorded from an initial luminance of 1000 cd m⁻² at room temperature by using an OLED lifetime tester (M6000 PMX, McScience). The photochemical stability was examined using a He–Cd laser (excitation wavelength = 325 nm, 3.5 mW, IK3202R‐D, KIMMON KOHA) with a fluorescent spectrometer (QE65 Pro, Ocean Optics).