Contribution of TADF and exciplex emission for efficient "warm-white" OLEDs

• The bicarbazole derivative 4,4'-(9H, 9'H-[3,3'-bicarbazole]-9,9'-diyl) bis(3-(trifluoromethyl) benzonitrile), denoted as pCNBCzoCF(3), was synthesized and tested for white OLED applications. pCNBCzoCF3 demonstrated an extremely small value of the singlet-triplet energy gap that caused intensive thermally activated delayed fluorescence (TADF). In addition, this compound is able to form exciplex-type excited states at the interface with star-shaped 4,40,400-tris[phenyl(m-tolyl) amino] triphenylamine (m-MTDATA). Combining the TADF emission of pCNBCzoCF3 with the exciplex emission from the pCNBCzoCF(3) m-MTDATA interface, we fabricated a number of highly efficient "warm-white'' OLEDs, the electroluminescence of which was close to candle emission. The best device demonstrated a very high brightness of 40 900 Cd m(-2) (at 15 V), current efficiency of 53.8 Cd A(-1) and power efficiency of 19.3 lm W-1, while the external quantum efficiency reached 18.8%. The fabricated devices demonstrated high emission characteristics even for the standard test at 1000 Cd m(-2) (current efficiency of 46.2 Cd A(-1), power efficiency of 10.6 lm W-1, EQE of 17.0%).

Ämnesord

NATURVETENSKAP  -- Kemi -- Materialkemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Materials Chemistry (hsv//eng)

Nyckelord

Light-Emitting-Diodes

Activated Delayed Fluorescence

Highly Efficient

Host Material

Derivatives

Carbazole

Electroluminescence

Enhancement

Conversion

Mechanism

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