Highly efficient orange and green solid-state light-emitting electrochemical cells based on cationic Ir(III) complexes with superior steric hindrance
Journal
Advanced Functional Materials
Journal Volume
17
Journal Issue
6
Pages
1019-1027
Date Issued
2007-04
Author(s)
Abstract
Abstract Highly efficient orange and green emission from single‐layered solid‐state light‐emitting electrochemical cells based on cationic transition‐metal complexes [Ir(ppy) 2 sb]PF 6 and [Ir(dFppy) 2 sb]PF 6 (where ppy is 2‐phenylpyridine, dFppy is 2‐(2,4‐difluorophenyl)pyridine, and sb is 4,5‐diaza‐9,9′‐spirobifluorene) is reported. Photoluminescence measurements show highly retained quantum yields for [Ir(ppy) 2 sb]PF 6 and [Ir(dFppy) 2 sb]PF 6 in neat films (compared with quantum yields of these complexes dispersed in m ‐bis( N ‐carbazolyl)benzene films). The spiroconfigured sb ligands effectively enhance the steric hindrance of the complexes and reduce the self‐quenching effect. The devices that use single‐layered neat films of [Ir(ppy) 2 sb]PF 6 and [Ir(dFppy) 2 sb]PF 6 achieve high peak external quantum efficiencies and power efficiencies of 7.1 % and 22.6 lm W –1 ) at 2.5 V, and 7.1 % and 26.2 lm W –1 at 2.8 V, respectively. These efficiencies are among the highest reported for solid‐state light‐emitting electrochemical cells, and indicate that cationic transition‐metal complexes containing ligands with good steric hindrance are excellent candidates for highly efficient solid‐state electrochemical cells.
Type
journal article