Singlet and triplet to doublet energy transfer: improving organic light-emitting diodes with radicals

Journal article

Organic light-emitting diodes (OLEDs) must be engineered to circumvent the efficiency limit imposed by the 3:1 ratio of triplet to singlet exciton formation following electron-hole capture. Here we show the spin nature of luminescent radicals such as TTM-3PCz allows direct energy harvesting from both singlet and triplet excitons through energy transfer, with subsequent rapid and efficient light emission from the doublet excitons. This is demonstrated with a model Thermally-Activated Delayed Fluorescence (TADF) organic semiconductor, 4CzIPN, where reverse intersystem crossing from triplets is characteristically slow (50% emission by 1 µs). The radical:TADF combination shows much faster emission via the doublet channel (80% emission by 100 ns) than the comparable TADF-only system, and sustains higher electroluminescent efficiency with increasing current density than a radical-only device. By unlocking energy transfer channels between singlet, triplet and doublet excitons, further technology opportunities are enabled for optoelectronics using organic radicals.

Authors: Li, F; Gillett, AJ; Gu, Q; Ding, J; Chen, Z

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Nature Research
• Journal: Nature Communications
• Volume: 13
• Issue: 1
• Pages: 2744-2744
• Article number: 2744
• Publication date: 2022-05-18
• DOI: 10.1038/s41467-022-29759-7
• EISSN: 2041-1723
• ISSN: 2041-1723
• Language: English
• Keywords: Radical; Chemistry; Condensed matter physics; Triplet state; Atomic physics; Intersystem crossing; Photochemistry; Optoelectronics; Diode; Exciton; Nanotechnology; Singlet fission; Singlet state; Electroluminescence; Physics; OLED; Excited state; Materials science