Unexpected large spectral shift from blue to green region in a light-emitting electrochemical cells

Henk J. Bolink, Eugenio Coronado, Rubén D. Costa, Nora Lardiés, Md K. Nazeeruddin, Enrique Ortí

研究成果: Conference contribution


A new, but archetype compound [Ir(ppy-F2)2Me 4phen]PF6, where ppy-F2 is 2-(2′, 4′-fluorophenyl)pyridine and Me4phen is 3,4,7,8-tetraraethyl-1, 10-phenanthroline, was synthesized and used to prepare a solid-state light-emitting electrochemical cell (LEC). This complex emits blue light with a maximum at 476 nm when photoexcited in a thin film, with a photoluminescence quantum yield of 52 %. It yields an efficient single-component solid-state electroluminescence device with a current efficiency reaching 5.5 cd/A and a maximum power efficiency of 5.8 Lm/Watt. However, the electroluminiscence spectrum is shifted with respect to the photoluminiscence spectrum by 80 nm resulting in the emission of green light. We demonstrate that this unexpected shift in emission spectrum is not originating from the way of excitation, nor from the presence of large concentrations of ions, but is related to the concentration of the ionic transition metal complex in the thin film. The origin of the concentration dependent emission is extensively commented and argued to be related to the population of either 3LC π-π* or 3MLCT triplet states, in diluted and concentrated films, respectively. Using quantum chemical calculations we demonstrate that three low-energy triplet states are present with only 0.1 eV difference in energy and that their associated emission wavelengths differ by as much as 60 nm from each other.

ホスト出版物のタイトルOrganic Optoelectronics and Photonics III
出版ステータスPublished - 2008
イベントOrganic Optoelectronics and Photonics III - Strasbourg, France
継続期間: 2008 4月 72008 4月 10


名前Proceedings of SPIE - The International Society for Optical Engineering


ConferenceOrganic Optoelectronics and Photonics III

ASJC Scopus subject areas

  • 電子材料、光学材料、および磁性材料
  • 凝縮系物理学
  • コンピュータ サイエンスの応用
  • 応用数学
  • 電子工学および電気工学


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