A computational scheme for evaluating the phosphorescence quantum efficiency: applied to blue-emitting tetradentate...

Area of Science:

• Materials Science
• Quantum Chemistry
• Organic Electronics

Background:

• Phosphorescent organic light-emitting diodes (PhOLEDs) are promising for displays and lighting.
• Blue phosphorescent tetradentate Pt(II) complexes are of significant interest due to their high efficiency and tunable structures.

Purpose of the Study:

• Investigate the triplet excited state energy surface and decay pathways of blue-emitting tetradentate Pt(II) complexes.
• Determine the dominant non-radiative decay mechanisms influencing phosphorescence quantum efficiency.

Main Methods:

• Employed quantum chemistry calculations combined with the thermal vibration correlation function (TVCF) formalism.
• Analyzed triplet excited state energy surfaces, direct vibrational relaxation, and minimum energy crossing points (MECPs) via transition states (³TS).

Main Results:

• Direct vibrational relaxation was found to be the dominant non-radiative decay pathway in most studied Pt(II) complexes.
• This dominance is attributed to high ³TS or unreachable MECPs.
• For specific complexes like PtON1-oMe with low ³TS and MECP, decay via MECP becomes dominant.

Conclusions:

• The TVCF formalism accurately predicts phosphorescence quantum efficiency by accounting for dominant decay mechanisms.
• Understanding the interplay between vibrational relaxation and MECP pathways is crucial for designing efficient blue PhOLED emitters.