2016/06/28 by Dawei Di, Alexander S. Romanov, Le Yang +9 · 2 citations
Chemistry · Engineering · Materials Science · Physics and Astronomy · #Luminescence and Fluorescent Materials #Organic Light-Emitting Diodes Research #Synthesis and Properties of Aromatic Compounds #cond-mat.mes-hall #cond-mat.mtrl-sci #physics.optics
paper · pdf · doi:10.1126/science.aah4345
published as Science 356, 159-163 (2017)
arxiv created 2016/06/28 · openalex created_date 2016/07/22 · openalex publication_date 2017/03/31 · arxiv updated 2018/04/18 · openalex updated_date 2026/08/04
The efficiency of an organic light-emitting diode (OLED) is fundamentally governed by the spin of recombining electron-hole pairs (singlet and triplet excitons), since triplets cannot usually emit light. The singlet-triplet energy gap, a key factor for efficient utilization of triplets, is normally positive. Here we show that in a family of materials with amide donor and carbene acceptor moieties linked by a metal, this energy gap for singlet and triplet excitons with charge-transfer character can be tuned from positive to negative values via the rotation of donor and acceptor about the metal-amide bond. When the gap is close to zero, facile intersystem crossing is possible, enabling efficient emission from singlet excitons. We demonstrate solution-processed LEDs with exceptionally high quantum efficiencies (near-100% internal and >27% external quantum efficiencies), and current and power efficiencies (87 cd/A and 75 lm/W) comparable to, or exceeding, those of state-of-the-art vacuum-processed OLEDs and quantum dot LEDs.