title: Exciplex-Sensitized Triplet-Triplet Annihilation in Heterojunction Organic Thin-Film.
abstract: A new concept for organic light-emitting diodes (OLEDs) is presented, which is called exciplex-sensitized triplet-triplet annihilation (ESTTA). The exciplex formed at the organic heterojunction interface of 4,4',4″-tris(N-3-methyphenyl-N-phenyl-amino) triphenylamine and 9,10-bis(2'-naphthyl) anthracene (ADN) is used to sensitize the triplet-triplet annihilation (TTA) process on the ADN molecules. This results in a turn-on voltage (2.2 V) of the blue emission from the OLED below the bandgap (2.9 eV). From the transient electroluminescence measurement, blue emission totally came from the TTA process without direct recombination on the ADN molecules. The blue singlet exciton from the TTA process can be quenched by energy transfer to the exciplex, as revealed by transient photoluminescence measurements. This can be prevented by blocking the energy transfer path and improving the radiative recombination rate of blue emission. With the insertion of the "triplet diffusion and singlet blocking (TDSB)" layer and the incorporation of the dopant material, an ESTTA-OLED with external quantum efficiency of 5.1% was achieved, which consists of yellow and blue emission coming from the exciplex and ESTTA process, respectively.
authors.affiliation: Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University , 1, Sec. 4, Roosevelt Road, Taipei, Taiwan, Republic of China , 10617.
authors.forename: Bo-Yen
authors.initials: BY
authors.lastname: Lin
authors.affiliation: Department of Chemistry, University of California, Riverside , Riverside, California 92506, United States.
authors.forename: Connor J
authors.initials: CJ
authors.lastname: Easley
authors.affiliation: Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University , 1, Sec. 4, Roosevelt Road, Taipei, Taiwan, Republic of China , 10617.
authors.forename: Chia-Hsun
authors.initials: CH
authors.lastname: Chen
authors.affiliation: Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University , 1, Sec. 4, Roosevelt Road, Taipei, Taiwan, Republic of China , 10617.
authors.forename: Po-Chen
authors.initials: PC
authors.lastname: Tseng
authors.affiliation: Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University , 1, Sec. 4, Roosevelt Road, Taipei, Taiwan, Republic of China , 10617.
authors.forename: Ming-Zer
authors.initials: MZ
authors.lastname: Lee
authors.affiliation: Center for Condensed Matter Science, National Taiwan University, and Institute of Atomic and Molecular Science, Academia Sinica , 1, Sec. 4, Roosevelt Road, Taipei, Taiwan, Republic of China , 10617.
authors.forename: Pin-Hao
authors.initials: PH
authors.lastname: Sher
authors.affiliation: Center for Condensed Matter Science, National Taiwan University, and Institute of Atomic and Molecular Science, Academia Sinica , 1, Sec. 4, Roosevelt Road, Taipei, Taiwan, Republic of China , 10617.
authors.forename: Juen-Kai
authors.initials: JK
authors.lastname: Wang
authors.affiliation: Department of Photonics Engineering, Yuan Ze University , 135 Yuan-Tung Road, Taoyuan, Taiwan, Republic of China , 32003.
authors.forename: Tien-Lung
authors.initials: TL
authors.lastname: Chiu
authors.affiliation: Department of Electro-Optical Engineering, National United University , 1, Lienda Road, Miaoli, Taiwan, Republic of China , 36003.
authors.forename: Chi-Feng
authors.initials: CF
authors.lastname: Lin
authors.affiliation: Department of Chemistry, University of California, Riverside , Riverside, California 92506, United States.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Bardeen
authors.affiliation: Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University , 1, Sec. 4, Roosevelt Road, Taipei, Taiwan, Republic of China , 10617.
authors.forename: Jiun-Haw
authors.identifier: http://orcid.org/0000-0003-3888-0595
authors.initials: JH
authors.lastname: Lee
keywords: Triplet−triplet annihilation; energy transfer; exciplex; organic light-emitting diode; upconversion