Extended Data Fig. 3: The delayed fluorescence after turn-off of electrical pulses for BTA3 based OLEDs.

a, Original waveform of generator produced electrical pulse, with a repetition rate of 1 kHz and a duty ratio of 1%. b, Delayed fluorescence after turn-off of electrical pulses of 1 A cm⁻² and 5 A cm⁻², and calculated turn-off responses at the respective singlet densities. The delayed fluorescence after turn-off suggests that a balance between singlet decay and singlet generation can be achieved at pulsed current density is 5 A cm⁻² such that the EL decay is governed by the decay of triplets (Supplementary Note 1 and Note Fig. 1). Prompt decay becomes dominant whenever the pulse current is smaller or larger than 5 A cm⁻² (Supplementary Note Fig. 2), which is governed by either nanosecond singlet decay (for an electrical pulse of 1 A cm⁻²) or enhanced TTA due to the increase in the triplet density, respectively. The monoexponential decay of the balanced delayed fluorescence gives a triplet decay rate (\({k}_{T}\)) of (7.5 ± 2.5)×10⁶s⁻¹ (triplet lifetime of 0.13 μs) (Supplementary Table 7). Fitting the delayed fluorescence at 5 A cm⁻² to the modified rate equations (equation 3 and equation 4, Supplementary Note 1) yields a TTA rate (\({k}_{{TT}}\)) of (2.0 ± 1.7)×10⁻¹⁰ cm³ s⁻¹.

Source data