Shedding light on the photophysical properties of newly designed platinum(II) complexes by adding substituents on functionalized ligands as highly efficient OLED emitters from a theoretical viewpoint

• The absorption and phosphorescence spectra of Pt(II) complexes are investigated.
• Their Φem, IP, EA, and reorganization energy are compared.
• Three new Pt(II) complexes are designed.

The phosphorescent properties of three synthesized and three new designed platinum(II) complexes are focused on in this work. To reveal their structure–property relationships, a density functional theory/time-dependent density functional theory (DFT/TDDFT) investigation is performed on the geometric and electronic structures, absorption and emission spectra. The electroluminescent (EL) properties are evaluated by the ionization potential (IP), electron affinity (EA), and reorganization energy (λ). Furthermore, the radiative rate constant (kr) is qualitatively elucidated by various factors including the strength of the SOC interaction between the higher-lying singlet excited states (Sn) and the T1 state, the oscillator strength (f) of the Sn states that can couple with the T1 state, and the energy separation between the coupled states. A combined analysis of various elements that could affect the phosphorescent efficiency is beneficial to exploring efficient triplet phosphors in OLEDs. Consequently, complexes Pt-1 and 1 would be more suitable blue-emitting phosphorescent materials with balance of EL properties and acceptable quantum yields.

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