山形大城戸・笹部研と華南理工大蘇教授との共同研究成果、外部量子効率35%を実現する超高効率TADF材料の記事が日経 xTECH に掲載されました。本記事は、2018年春の第６５回応用物理学会春季学術講演会で卒業生の小松龍太郎君が「スピロビアクリジン含有水平配向性TADF材料を用いた超高効率有機EL素子」のタイトルで発表した内容がもとになっています。棒状のスピロビアクリジン骨格誘導体TADF発光材料が基板水平配向することを利用して、有機EL素子の外部量子効率を飛躍的に向上させ、リン光材料と同等の効率を実現しました。本研究は、ROEL の横山大輔准教授、INOEL の硯里善幸准教授にも有機固体薄膜中の分子配向評価・解析の面からご協力頂きました！ACS Chemistry of Materials に掲載された原著論文のアブストラクトは以下の通りです。
Title: Horizontally Orientated Sticklike Emitters: Enhancement of Intrinsic Out-Coupling Factor and Electroluminescence Performance
By M. Liu, R. Komatsu, X. Cai, K. Hotta, S. Sato, K. Liu, D. Chen, Y. Kato, H. Sasabe*, S. Ohisa, Y. Suzuri, D. Yokoyama, S.-J. Su*, J. Kido,* Chem. Mater.2017, 29, 8630–8636.
Abstract: Highly efficient organic light-emitting diodes are in urgent demand in applications of new generation full-color displays and solid-state lighting sources. The limitation of device performance is greatly affected by extrinsic and intrinsic elements of the light out-coupling process. By elaborately designing emitters as sticklike molecules, horizontal orientation ratios in the range of 86–93% were realized to intrinsically increase the out-coupling factor of electroluminescence devices. These elongated compounds are inclined to lie parallel to substrate in vacuum-deposited thin solid films and regularize their transition dipole moments in a major degree. As consequences of such desirable molecule arrangement, remarkable external quantum efficiencies near 21% for pure blue devices, close to 30% for sky-blue devices, and over 35% for greenish blue devices were respectively achieved. A compatible strategy on devising high-performance emitters for organic electroluminescence is advocated herein.
