A novel blue thermally activated delayed fluorescence (TADF) organic light-emitting diode with an emitting layer made up of a TADF assistant dopant and a pure blue-emitting TADF emitter was developed.

In this study, four emitters of blue light are synthesized by selecting pyrene with its high photoluminescence quantum yield (PLQY) as the core group and variants of the electron-donating diphenylamine (DPA) as side groups. The four compounds have different numbers, sizes, and substitution positions of alkyl groups on the DPA. Each of the four compounds when doped in OLED devices shows a high current efficiency (CE) of over 7 cd A and a high external quantum efficiency (EQE) of over 7.5%. In addition, the compounds yield electroluminescence (EL) spectra showing peaks with narrow full width at half-maximum (fwhm) values of 37-40 nm and hence indicative of high color purity. Moreover, one compound N1,N6-bis(5-( tert-butyl)-2-methylphenyl)-N1,N6-bis(2,4-dimethylphenyl)pyrene-1,6-diamine (3Me-1Bu-TPPDA), shows a very high EQE of 9.25% and a very long lifetime with an LT95 of 471 h.

Highly efficient deep blue fluorescent material and various thermally activated delayed fluorescent (TADF) blue sensitization materials were synthesized for fluorescent deep blue organic light-emitting diodes (OLEDs). These materials were designed and selected by considering efficient energy transfer conditions (i.e., spectral overlap and quantum efficiency) between sensitizer and acceptor. Energy transfer process from TADF host sensitizers to deep blue fluorescent emitter has been investigated by measuring the energy transfer rate. Measured energy transfer rate was to be 1.24 × 10 s (mol/dm) for a prompt decay of fluorescence and 2.61 × 10 s (mol/dm) for delayed fluorescence, which demonstrated the efficient energy transfer. Indeed, highly efficient deep blue fluorescent OLEDs boosted by the TADF host-sensitization process were successfully fabricated. The maximum external quantum efficiency was 19.0% with color coordinates of (0.14, 0.15) and 15.5% with color coordinates of (0.15, 0.11) in the different host system. The efficiency roll-off characteristic and device operating lifetime were also improved by this efficient sensitization process.

Design of an optical pattern in a light-guide panel ͑LGP͒ has relied on empirical methods. However, the characteristics of developing liquid-crystal display ͑LCD͒ products such as frequent design modifications, various design conditions, and a short development period make it difficult for the empirical design approach to cope with various design requirements for size, shape, and optical performance of the LCD products. The most important tasks for the design of LGPs are improving average illuminance and the uniformity of the backlight unit. To meet these requirements, a design for an incoupling and an outcoupling part of the LGP is presented. These two parts can be designed in two separate phases: the first for the incoupling part and the second for the outcoupling part. The shape of serration in the incoupling part was first determined by design of experiments, and the dot patterns in the outcoupling part were subsequently determined by a density-based approach with progressive quadratic response surface modeling. Using this design approach, the illuminance was increased from 2241 lx in the initial design to 2299 lx in the optimal design, and its uniformity also increased from 38% to 82%.