Thermally Activated Delayed Fluorescence Warm White Organic Light Emitting Devices with External Quantum Efficiencies Over 30

• Published in: Advanced functional materials Vol. 31; no. 31
• Main Authors: Chen, Jia‐Xiong, Wang, Kai, Xiao, Ya‐Fang, Cao, Chen, Tan, Ji‐Hua, Wang, Hui, Fan, Xiao‐Chun, Yu, Jia, Geng, Feng‐Xia, Zhang, Xiao‐Hong, Lee, Chun‐Sing
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01-08-2021
• Subjects: Color; Emitters; Energy transfer; Excitons; Fluorescence; Materials science; Organic light emitting diodes; Phosphorescence; single emitting‐layer; thermally activated delayed fluorescence; white organic light‐emitting diodes
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202101647

While monochrome organic light‐emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) emitters have achieved over 30% external quantum efficiencies (EQEs), all‐TADF white OLEDs (WOLEDs) are still lagging behind. Herein, a simple system based on two color‐complementary TADF emitters is exploited to realize high‐performance WOLEDs. By doping a high‐performance orange–red TADF fluorophor (BPPZ‐DPXZ) into a blue TADF host (DBFCz‐Trz), energy transfer, and triplet‐to‐singlet conversion in the host‐dopant system can be optimized to simultaneously achieve full exciton utilization and color balance. With this design, all‐TADF single‐emitting‐layer WOLEDs with a maximum EQE up to 32.8% are demonstrated. This high efficiency surpasses EQEs of reported WOLEDs based on both TADF as well as phosphorescence. It is expected that this finding can provide new insight for designing highly efficient all‐TADF WOLEDs.
All thermally activated delayed fluorescence (TADF) single‐emitting‐layer white organic light‐emitting diodes are developed by using a high‐efficiency orange–red TADF fluorophor doped in a blue TADF fluorophor. Singlet and triplet excitons in the devices can be well shared and captured in two emitters, resulting in state‐of‐the‐art performances with maximum external quantum efficiencies of over 30%.