Strategically Modulating Carriers and Excitons for Efficient and Stable Ultrapure‐Green Fluorescent OLEDs with a Sterically Hindered BODIPY Dopant

Abstract

Ultrapure colors are vital for displays to obtain the highly desired wide color‐gamut. Till now, only boron‐dipyrromethene derivatives (BODIPYs) have demonstrated ultrapure full‐colors but suffer from low excitons utilization efficiency as dopants in organic light‐emitting diodes. It is proposed here that with a thermally activated delayed fluorophore to sensitize BODIPYs, all excitons can be recycled, which, still, is challenged by exciton loss through Dexter energy transfer (DET) from sensitizer to dopant and direct charge trapping on BODIPYs. Hence, a sterically hindered BODIPY‐type dopant with a bulk substituent on the meso‐position is developed to suppress DET, exhibiting a high photo‐luminance quantum yield of 98% and a small full width at half maximum of 28 nm. Moreover, the device structure is elaborately designed, successfully modulating carriers and excitons to avoid charge trapping on dopant and also trigger multiple‐sensitizing processes to reduce exciton loss. Consequently, a state‐of‐the‐art maximum external quantum efficiency/power efficiency of 19.0%/85.7 lm W−1 are realized together with an ultrapure‐green emission of Commission Internationale de l'Eclairage coordinates of (0.26, 0.67) and a long half‐lifetime of 2947 h at an initial luminance of 1000 cd m−2.

Hyperfluorescent polymers enabled by through-space charge transfer polystyrene sensitizers for high-efficiency and full-color electroluminescence

“…Moreover, V on s are independent of emitter contents of polymers, suggesting that energy transfer from the TSCT polymer to emitter, rather than direct charge trapping by the emitter, plays a dominant role in exciton formation under electrical excitation. 51 This observation is consistent with energy level alignment for TSCT polymers and emitters. As shown in Fig.…”

“…Moreover, the V on s are independent on emitter contents of polymers, suggesting that energy transfer from TSCT polymer to emitter, rather than direct charge trapping by emitter, plays dominant role in exciton formation under electrical excitation. [51] This observation is consistent with energy level alignment for TSCT polymers and emitters. As shown in Figure 4a, HOMO levels of PhPe and NTTPA are lower than those of corresponding TSCT polymers (BP-H and RP-H), while LUMO level of TBPAD is higher than that of GP-H. That is, energy levels of emitters are not located in the gap between HOMO and LUMO of TSCT polymers, which can avoid charge trapping by emitters.…”

“…As the emitter content grows, the relative emission intensity between emitter and TSCT polymer increases, indicating that Förster energy transfer from sensitizer to emitter is more efficient at higher emitter content. [11,51] Meanwhile, it is found that emissions of TSCT polymers are completely quenched at emitter content of 1.0 mol% for blue and green polymers, but there is still emission residue from TSCT polymer for red polymers at the same emitter content (Figure 2g-i). In fact, the FRET integral ( ) between absorption of emitter and emission of sensitizer can be calculated by following equation:…”

Organic color‐conversion media for full‐color micro‐LED displays

“…Together with a blue LED, the CCM scheme can be used to achieve almost 100% sRGB color space for display applications as shown in Figure 9 and to potentially reach the DCI-P3 standard by adopting a green emitter with a sharper PL spectrum. 20,21 DMP and the selected green and red dopants are naturally compatible with shadow masking techniques for fabricating CCM films. However, the current fine metal mask (FMM) used in the OLED industry is only around 500 ppi and ultimately limited to under 1000 ppi by its larger-than-10-μm thickness.…”

Achieving High Efficiency and Pure Blue Color in Hyperfluorescence Organic Light Emitting Diodes using Organo-Boron Based Emitters

“…The exact rate constants of FRET in HF system were calculated by using following equation (2). [25][26] = − , −…”