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

Gu, Qinying 
Ding, Junshuai 
Chen, Zhangwu 

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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.

Publication Date
Online Publication Date
Acceptance Date
Article, /639/624/1020/1091, /639/301/1019/1020/1091, /120, /140/125, /140/58, /128, article
Journal Title
Nat Commun
Journal ISSN
Volume Title
Nature Publishing Group UK
Engineering and Physical Sciences Research Council (EP/M005143/1)
Engineering and Physical Sciences Research Council (EP/M01083X/1)
European Research Council (670405)
European Commission Horizon 2020 (H2020) ERC (101020167)