U 3900 scanning spectrophotometer

All the organic and inorganic materials used in this study were purchased from commercial sources and used without further purification. All OLEDs were fabricated on indium tin oxide (ITO)-coated glass substrates with a sheet resistance of 10 Ω sq⁻¹. The organic layers were deposited at a rate of 1.0 Å s⁻¹, and the inorganic layers of MoO₃ and LiF were deposited at a rate of 0.1 Å s⁻¹. An Al cathode was deposited in the end at a rate of 5.0 Å s⁻¹ with a shadow mask, which defined a device area of 3 × 3 mm². The photoluminescence (PL) spectra were measured using a FluoroMax-4 fluorescence spectrometer (HORIBA Jobin Yvon). The UV-Vis absorption spectrum was recorded using a Hitachi U-3900 scanning spectrophotometer. The electroluminescence (EL) spectra were measured through a computer controlled PR-655 Spectra Scan spectrometer. The current–voltage–luminance curves were measured with Keithley 2400 power supply combined with a BM-7A luminance colorimeter. External quantum efficiency (EQE) was calculated from the current density–voltage–luminance curve and spectral data. Besides, all measurements were carried out at room temperature and under ambient conditions without any protective coatings.

All the devices were fabricated on indium tin oxide (ITO) coated glass substrates with a sheet resistance of 10 Ω sq⁻¹. The ITO substrates were cleaned with acetone, deionized water, and acetone, in sequence, and then, treated by ultraviolet-ozone for 15 min. Subsequently, the ITO substrates were loaded into a high vacuum chamber (approximately 3 × 10⁻⁴ Pa) for subsequent deposition. After the deposition of organic–inorganic layers, Al cathode was deposited in the end with a shadow mask, which defined the device area of 3 × 3 mm². The UV-vis absorption spectrum was measured with a Hitachi U-3900 scanning spectrophotometer. The photoluminescence (PL) spectra were measured with a FluoroMax-4 fluorescence spectrometer (HORIBA Jobin Yvon). The electroluminescent (EL) spectra were measured using a PR-655 spectra scan spectrometer with computer control. The current–voltage–luminance characteristics were measured by a measuring system of the Keithley 2400 power supply combined with a BM-7A luminance colorimeter. EQE was calculated from the EL spectra data and current density–voltage–luminance curve. All the materials were procured commercially and used without further purification. All the measurements were carried out at room temperature and under ambient conditions without any protective coatings.