Investigation of a sterically hindered Pt(II) complex to avoid aggregation-induced quenching: Applications in deep red electroluminescent and electrical switching devices

- Reduction of aggregation-induced phosphorescence quenching in thin solid film by Tert-butyl substituents on Pt(II) complex.
- Efficient deep red OLEDs with CIE of (0.69, 0.3).
- Negative differential resistance with ON/OFF current ratio higher than 103.

Thanks to its deep-red emission, [Pt(II)(tetra-tert-butylSalophen)] 1 is used as a dopant in Tris-(8-hydroxyquinoline)aluminium (Alq3) for the fabrication of organic light-emitting diodes (OLEDs). This complex is compared to the alike [Pt(II) Salophen] 2. Energy levels of HOMO and LUMO determined by cyclic voltammetry and DFT calculation are in good accordance for energy transfer from Alq3 to 1 or 2. A stable color (Commission Internationale de l'Energie (CIE) coordinates of (0.69, 0.3)) with performance (605 Cd/m2 and 755 A/m2 at 14 V) and an external quantum efficiency (EQE) of 21% were obtained when adding N,N′-Di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPD) as hole collector. Optoelectrical studies evidence an improvement of the electroluminescence performance due to the reduction of the aggregation-induced quenching in complex 1 based thin solid film. Furthermore, a negative differential resistance (NDR) characteristic is observed on monolayer based devices at low voltage region upon electrical driving stress, with an ON/OFF current ratio higher than 103, suggesting a potential application in organic memory devices.

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