Highly Efficient Spiro[fluorene-9,9′-thioxanthene] Core Derived Blue Emitters and Fluorescent/Phosphorescent Hybrid White Organic Light-Emitting Diodes

Abstract

A series of blue emitters incorporating spiro­[fluorene-9,9′-thioxanthene] or spiro­[fluorene-9,9′-thioxanthene-S,S-dioxide] as the core and phenylcarbazole or triphenylamine as the arms were designed and synthesized. Their spiro conformation is beneficial for their thermal stability and for reducing the trend of aggregation quenching. By tuning the valence of the sulfur atom, highly efficient local excited (LE) state deep blue emitters and charge-transfer (CT) state blue emitters are obtained. The devices based on the LE emitters TPA-S and CzB-S as the nondoped emissive layer exhibit high external quantum efficiency of 1.76% and 2.03% and Commission Internationale de l’Eclairage (CIE) coordinates of (0.158, 0.039) and (0.160, 0.054), respectively, and their CIE y values are among the smallest ever reported for the deep blue OLEDs and are readily very close to that of the inorganic light-emitting diode [CIE (0.16, 0.02)]. The nondoped device based on the CT emitter TPA-SO2 as the emissive layer also exhibits a high current efficiency of 5.46 cd A–1 and CIE coordinates of (0.154, 0.168). To fully utilize the 25% singlet and 75% triplet excitons, fluorescent/phosphorescent hybrid white organic light-emitting diodes in a single-emissive-layer architecture were also fabricated with TPA-SO2 as the blue emitter as well as the host of orange phosphorescent emitter to give forward-viewing power efficiency of 47.9 lm W–1, which is the highest value ever reported for the devices in a similar architecture without using any out-coupling technology.

Thermally Activated Delayed Fluorescence Emitters for Deep Blue Organic Light Emitting Diodes: A Review of Recent Advances

“…The high electronegativity of the oxygen atoms results from the electron withdrawing ability of the DPS moiety. In addition, the DPS group exhibits a tetrahedral geometry and the S atom has an isolating nature, which efficiently limits the conjugation within the compounds [65]. For this reason, DPS has become a popular electron-accepting group for researchers that are aiming at designing TADF emitters.…”

9H‐Quinolino[3,2,1‐k]phenothiazine: A New Electron‐Rich Fragment for Organic Electronics

“…In this context, the widely known electron rich carbazole fragment has led to impressive breakthroughs and is nowadays an important building block in organic electronics. [11,12] Around the molecular structure of carbazole, many other carbazole-like fragments have been developed in the recent years sometimes surpassing the performance of the carbazole fragment in electronics. Thus, indolocarbazole (IC), [13] phenylacridine (PA) [14][15][16] and more recently indoloacridine (IA) [17] are nowadays key building blocks, widely used in all organic electronic devices.…”

Efficient fluorescence/phosphorescence white organic light-emitting diodes with ultra high color stability and mild efficiency roll-off

“…The performance of the blue device is comparable with the best reported fluorescent results at the similar CIE coordinates. [22][23][24][25][26] NAA based blue fluorescent device has demonstrated a high luminous efficiency and a pure blue emission meeting the needs of white-light illumination. Hence, F/P WOLEDs (device W1), using NAA as the blue fluorescent dopant, Ir (2-phq) 3 as orange dopant, and Ir(ppy) 3 as green dopant, have been fabricated.…”