The role of the bulky blocking unit of the fluorescent emitter in efficient green hyper-fluorescent organic light-emitting diodes

Figures & data

Figure 1. The emission mechanism of hyper-fluorescent OLEDs.

Figure 2. Molecular structure of fluorescent emitters and sensitizer.

Figure 3. (a) The absorption spectra and emission spectra of the fluorescent emitters and TADF sensitizer in THF solutions, and (b) The emission spectra of the fluorescent emitters and TADF sensitizer doped films with DPEPO host.

Table 1. The photophysical properties of the TADF sensitizer and the fluorescent emitters.

		λemission^b)
Name	λabsorption^a)	Solution	Film	HOMO^C)	LUMO^C)
TCzTrzDBF	–	531 nm (450 nm)	491 nm (435 nm)	−5.87 eV	−3.43 eV
6tBPA	461 nm	523 nm (479 nm)	523 nm (477 nm)	−5.98 eV	−2.74 eV
PhtBuPAD	469 nm	532 nm (489 nm)	529 nm (481 nm)	−5.25 eV	−2.83 eV

^a)Maximum wavelength of UV-Vis absorption spectra ^b)Maximum wavelength of emission spectra and numbers in parentheses indicate the onset wavelength of the emission spectra ^c)ref. [15,16].

Figure 4. The transient PL decay of the TCzTrzDBF and TADF sensitized fluorescent emitter films.

Table 2. The delayed fluorescent lifetime and the PLQY of the films.

Name	Delayed fluorescent lifetime (µs)	PLQY (%)
TCzTrzDBF	4.38	96.5
TCzTrzDBF: PhtBuPAD(1%)	2.72	96.6
TCzTrzDBF: PhtBuPAD(2%)	1.69	87.2
TCzTrzDBF: 6tBPA(1%)	2.40	99.5
TCzTrzDBF: 6tBPA(2%)	1.30	98.9
PhtBuPAD	–	77.0
6tBPA	–	84.7

Figure 5. Device structure and energy level diagram of the devices.

Figure 6. Device performances of the devices: (a) Current density-voltage-luminance curves, (b) EL spectra, (c) EQE-luminance curves, and (d) Current efficiency-luminance curves.

Table 3. The device performances of the hyper-fluorescent OLED.

	EQE (%)			Current efficiency (cd/A)
Name	Max	3000 cd/m^2	EQE roll-off	Max	3000 cd/m^2	Current efficiency roll-off	CIE (x,y)
TCzTrzDBF	26.0	11.6	55%	68.6	29.6	57%	(0.21, 0.43)
TCzTrzDBF: PhtBuPAD(1%)	18.1	9.6	47%	60.8	31.4	48%	(0.27, 0.56)
TCzTrzDBF: PhtBuPAD(2%)	13.3	9.0	32%	47.8	31.4	34%	(0.29, 0.59)
TCzTrzDBF: 6tBPA(1%)	16.7	8.4	49%	54.6	26.3	52%	(0.24, 0.54)
TCzTrzDBF: 6tBPA(2%)	12.6	7.1	44%	45.0	24.4	46%	(0.27, 0.60)

D. Zhang, X. Song, M. Cai, and L. Duan, Adv. Mater 30 (6), 1705250 (2018).

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J.G. Yu, S.H. Han, H.L. Lee, W.P. Hong, and J.Y. Lee, J. Mater. Chem. C 7 (10), 2919–2926 (2019).

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