An object is to provide a light-emitting element with a favorable lifetime.
A light-emitting element which includes a first electrode, a second electrode, and an EL layer and in which the EL layer includes a hole-injection layer and first to fourth layers; the hole-injection layer includes an organic acceptor and is positioned between the first electrode and the first layer; the first layer includes a first hole-transport material; the second layer includes a second hole-transport material and is positioned between the first layer and the third layer; the third layer includes a third hole-transport material; the fourth layer includes a host material and a light-emitting material and is positioned between the third layer and the second electrode; the HOMO level of the second hole-transport material is deeper than the HOMO level of the first hole-transport material; the HOMO level of the host material is deeper than the second hole-transport material HOMO level; the HOMO level of the third hole-transport material is deeper than or equal to the HOMO level of the host material; a difference between the HOMO level of the second hole-transport material and the HOMO level of the third hole-transport material is less than or equal to 0.3 eV; and the second hole-transport material is a triarylamine compound having a structure where a dibenzofuran skeleton or a dibenzothiophene skeleton is bonded to nitrogen of an amine directly or via a divalent aromatic hydrocarbon group.
本发明旨在提供一种寿命良好的发光元件。一种发光元件包括第一电极、第二电极和EL层,其中EL层包括注孔层和第一至第四层;注孔层包括有机受体,并位于第一电极和第一层之间;第一层包括第一孔传输材料;第二层包括第二孔传输材料,并位于第一层和第三层之间;第三层包括第三孔传输材料;第四层包括主体材料和
发光材料,并位于第三层和第二电极之间;第二孔传输材料的HOMO能级比第一孔传输材料的HOMO能级深;主体材料的HOMO能级比第二孔传输材料的HOMO能级深;第三孔传输材料的HOMO能级比主体材料的HOMO能级深或相等;第二孔传输材料的HOMO能级和第三孔传输材料的HOMO能级之间的差异小于或等于0.3 eV;第二孔传输材料是一种三芳基胺化合物,其结构中
二苯并呋喃骨架或
二苯并噻吩骨架直接或通过二价
芳香烃基团与胺氮结合。