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1. (WO2017037559) LIGHT-EMITTING ELEMENT, LIGHT-EMITTING DEVICE, ELECTRONIC DEVICE, AND LIGHTING DEVICE

Pub. No.:    WO/2017/037559    International Application No.:    PCT/IB2016/054941
Publication Date: Fri Mar 10 00:59:59 CET 2017 International Filing Date: Fri Aug 19 01:59:59 CEST 2016
IPC: H01L 51/50
Applicants: SEMICONDUCTOR ENERGY LABORATORY CO., LTD.
Inventors: SUZUKI, Tsunenori
TAKITA, Yusuke
SEO, Satoshi
Title: LIGHT-EMITTING ELEMENT, LIGHT-EMITTING DEVICE, ELECTRONIC DEVICE, AND LIGHTING DEVICE
Abstract:
A light-emitting element including a first electrode, a second electrode, and an EL layer positioned therebetween is provided. The EL layer includes a stack of a hole-injection layer, a first layer, a second layer, a third layer, and a fourth layer; the hole-injection layer includes an organic acceptor; the first layer, the second layer and the third layer include first, second and third hole-transport materials, respectively; and the fourth layer includes a host material and a light-emitting material; the HOMO level of the second hole-transport material is deeper than that of the first hole-transport material; the HOMO level of the host material is deeper than that of the second hole-transport material; the HOMO level of the third hole-transport material is deeper than or equal to that of the host material; and a HOMO level difference between the second and third hole-transport materials is less than or equal to 0.3 eV.