Ultrapure Blue Phosphorescent Organic Light-Emitting Diodes Employing a Twisted Pt(II) Complex

Described herein is a stable complex, Pt(mpzpyOczpy-mesi), embodying efficient, narrow blue emission. The highly twisted structure of the complex improves the stability and efficiency of photo- and electroluminescence by reducing the intermolecular interactions. The complex in solution shows high photoluminescence efficiency (>95%) and radiative decay rate (K_r = 2.9 × 10⁵ s^-1) with a narrow emission spectrum. The bottom-emitting phosphorescent device, BE1, exhibits durable deep blue emission with CIE coordinates of (0.145, 0.166) and 5.2 h of LT₅₀ at an initial luminance of 685 cd/m². Top-emitting devices, TE1 and TE2, achieve ultrapure blue color with CIE values of (0.141, 0.068) and (0.140, 0.071), respectively. TE4 shows high brightness of 3405 cd m^-2 at 50 mA m^-2, EQE of 10.2% at 1000 cd/m², and almost negligible color deviation around (0.135, 0.096) at viewing angles of 0°-60°.