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Modulation of Solid‐State Aggregation of Square‐Planar Pt(II) Based Emitters: Enabling Highly Efficient Deep‐Red/Near Infrared Electroluminescence
Author(s) -
Chen WenCheng,
Sukpattanacharoen Chattarika,
Chan WeiHsiang,
Huang ChunChi,
Hsu HsiuFu,
Shen Dong,
Hung WenYi,
Kungwan Nawee,
Escudero Daniel,
Lee ChunSing,
Chi Yun
Publication year - 2020
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.202002494
Subject(s) - electroluminescence , materials science , stacking , excited state , chromophore , photochemistry , trimer , steric effects , luminescence , dimer , monomer , phosphor , chemical physics , optoelectronics , nanotechnology , stereochemistry , chemistry , atomic physics , polymer , organic chemistry , physics , layer (electronics) , composite material
The design of square‐planar Pt(II) complexes with highly efficient solid‐state near infrared (NIR) luminescence for electroluminescence is attractive but challenging. This study presents the fine‐turning of excited‐state properties and application of a series of isoquinolinyl pyrazolate Pt(II) complexes that are modulated by steric demanding substituents. It reveals that the bulky substituents do not always disfavor metallophilic Pt···Pt interactions. Instead, π–π stacking among chelates, which are fine‐tuned by the associated substituents, also exerts strong influence to the metal‐metal‐to‐ligand charge transfer (MMLCT) transition character. Theoretical calculations indicate that Pt···Pt contacts become more relevant in the trimers rather than the dimers, especially in their T 1 states, associated with a change from mixed 3 LC/ 3 MLCT transition in the monomer/dimer to mixed 3 LC/ 3 MMLCT transition character in the trimer. Electroluminescence devices affording intense deep‐red/NIR emission (near 670 nm) with unprecedentedly high external quantum efficiency over 30% are demonstrated. This work provides deep insights into formation MMLCT transition of square‐planar Pt(II) complexes and efficient molecular design for deep‐red/NIR electroluminescence.