In situ-formed tetrahedrally coordinated double-helical metal complexes for improved coordination-activated n-doping

Ziyang Liu; Xiao Li; Yang Lu; Chen Zhang; Yuewei Zhang; Tianyu Huang; Dongdong Zhang; Lian Duan

doi:10.1038/s41467-022-28921-5

In situ-formed tetrahedrally coordinated double-helical metal complexes for improved coordination-activated n-doping

Nat Commun. 2022 Mar 8;13(1):1215. doi: 10.1038/s41467-022-28921-5.

Authors

Ziyang Liu¹, Xiao Li¹, Yang Lu², Chen Zhang¹, Yuewei Zhang^{1

3}, Tianyu Huang¹, Dongdong Zhang^{4

5}, Lian Duan^{6

7}

Affiliations

¹ Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China.
² Institute of Drug Discovery Technology, Ningbo University, Ningbo, 315211, China.
³ Center for Flexible Electronics Technology, Tsinghua University, Beijing, 100084, China.
⁴ Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China. ddzhang@mail.tsinghua.edu.cn.
⁵ Center for Flexible Electronics Technology, Tsinghua University, Beijing, 100084, China. ddzhang@mail.tsinghua.edu.cn.
⁶ Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China. duanl@mail.tsinghua.edu.cn.
⁷ Center for Flexible Electronics Technology, Tsinghua University, Beijing, 100084, China. duanl@mail.tsinghua.edu.cn.

Abstract

In situ coordination-activated n-doping by air-stable metals in electron-transport organic ligands has proven to be a viable method to achieve Ohmic electron injection for organic optoelectronics. However, the mutual exclusion of ligands with high nucleophilic quality and strong electron affinity limits the injection efficiency. Here, we propose meta-linkage diphenanthroline-type ligands, which not only possess high electron affinity and good electron transport ability but also favour the formation of tetrahedrally coordinated double-helical metal complexes to decrease the ionization energy of air-stable metals. An electron injection layer (EIL) compatible with various cathodes and electron transport materials is developed with silver as an n-dopant, and the injection efficiency outperforms conventional EILs such as lithium compounds. A deep-blue organic light-emitting diode with an optimized EIL achieves a high current efficiency calibrated by the y colour coordinate (0.045) of 237 cd A^-1 and a superb LT95 of 104.1 h at 5000 cd m^-2.