Near-infrared Organic Light-Emitting Diodes Based on Highly Horizontally Oriented Platinum Complex

Abstract

Recently, near-infrared (NIR) light sources have taken a great interest in the field of healthcare and wearable devices since NIR light sources can be used for various functionalities that visible light sources cannot do. In this regard, several works have recently been dedicated to the field of NIR OLEDs to enhance their performances and increase the emission wavelength towards longer wavelengths beyond 700 nm. However, the device performance of the NIR OLEDs still lags behind compared to the visible OLEDs. Here, we have designed a planar type Pt(II)-based phosphorescent molecule that emits light in the NIR region over 740 nm. These Pt(II) complexes are designed to have a perfect square planar (PSP) structure that can stack almost parallel to each other in the condensed phase through Pt···Pt interactions, thus increasing the metal-metal-to-ligand charge transfer (MMLCT) characteristics. The fabricated NIR OLEDs using the Pt(II) complex showed a maximum external quantum efficiency (EQE) of 5.2 % and maximum radiance of 120.7 W/m2/sr with an emission peak at 741 nm using the optimized device structure, illustrating that the proposed Pt(II) based NIR emitters have a great potential to be used for various applications with practically viable characteristics.