Near-Infrared Phosphorescent Organic Light-Emitting Diodes using Perfect Square Planar type cis-Pt(II) Complex

Abstract

Healthcare and wearable devices have taken a great interest in the field of near-infrared (NIR) light sources since they can provide various functionalities that visible light sources cannot do. With the various benefits of organic materials, such as flexibility and the possibility to make them in a large area, research on NIR organic lightemitting diodes (OLEDs) is regarded more and more important in the fields of OLEDs. Hence great attention has recently been paid to the field of NIR OLED to enhance their efficiencies as well as to increase the emission wavelength towards longer wavelengths beyond 700 nm. However, the device performance still lags behind when compared to OLEDs in the visible spectral range. To overcome the low performance of the NIR OLEDs, we have designed a new type of Pt(II)-based phosphorescent molecule that emits light in the NIR region over 800 nm. These Pt(II) complexes are designed to have a perfect square planar (PSP) structure that can stack parallel to each other in the solid-state through Pt···Pt interactions and subsequently enhance the metal-metal-to-ligand charge transfer (MMLCT) character. These PSP type Pt(II) emitters are utilized for the fabrication of NIR OLEDs and display a maximum external quantum efficiency of 2.5 % with an emission centered at 841 nm. These results in the study give solid support for the development of Pt(II) based near-IR emitters for various applications.