Fig. 1. Energy level diagram of materials used in the devices, and the chemical structures of Firpic and PO-01-TB.

Fig. 2. Structure schematic of devices A−D.

Fig. 3. UV-vis absorption and PL spectra of the deposited films.

Fig. 4. Normalized EL spectra of devices A−D at 20 mA/cm²

Fig. 5. (a) Structure schematic of hole-only devices H1−H4 and electron-only devices E1-E4; current density-voltage characteristics of (b) hole-only devices H1−H4 and (c) electron-only devices E1−E4.

Fig. 6. Normalized EL spectra of devices A(a) and B(b) with different voltage. Inset is the corresponding enlarged spectra at 540−570 nm.

Fig. 7. Luminance-voltage characteristics of devices A and B. Inset is EQE-luminance characteristic of devices A and B

Fig. 8. (a) Energy diagram and exciton dynamics of the WOLEDs W1 and W2. S₁ and T₁ are respectively the singlet (○) and triplet (△) energy levels, and S₀ is the ground state (○). The blue dashed box depicts the main region of carrier recombination. Luminance-voltage characteristics and the normalized EL spectra (b), and current efficiency-Luminance-external quantum efficiency characteristics (c) of the WOLEDs W1 and W2; (d) EQE-current density of the OLEDs B and W2. The red and blue lines are corresponding fitting curves based on the TTA model, respectively.

Fig. 9. Normalized EL spectra and the corresponding CIE coordinates, CRI of the device W2 at brightness of 1000−5000 cd/m².