Journal Article

Unveiling the Interfacial Properties of Organic Single‐Crystal Hole‐Transporting Layers for High‐Performance Light‐Emitting Devices

Wang, Xi‐Bin, Fang, Hong‐Hua, Liu, Yu, Liu, Yue‐Feng, Sun, Lingjie, Li, Yansong, Liu, Ze‐Qing, Xu, Bin, Du, Xiaobo, Ye, Gao‐Da, Zhang, Hu, Feng, Jing, Ding, Ran, Wang, Lei, Guo, Runda, Yang, Fangxu, Li, Su‐Heng

2025

Overview

Organic single crystals with long‐range molecular periodic ordering ensure superior charge‐transport properties and low defect density, which have been considered promising candidates for charge‐transporting materials in organic light‐emitting devices (OLEDs). The functional interfaces of OLEDs play a critical role in charge‐transporting and light‐emitting behaviors, while the interfacial properties of organic single crystals in OLEDs and their impact on device performance have been rarely investigated. Herein, two typical organic single crystals, 1,4‐bis(4‐Methylstyryl)benzene (BSB‐Me) and 2,6‐diphenylanthracene (DPA) with different molecular formulas and packing structures, are introduced as the single‐crystal hole‐transporting layers (HTLs) for a systematic investigation of the interfacial properties between single‐crystal HTLs and active emissive layers. BSB‐Me single‐crystal HTLs offer satisfied surface wettability and enhanced interfacial interaction, which dominate the charge‐transporting and light‐emitting behaviors of the OLEDs. Such improved interfacial properties are responsible for the superior light out‐coupling efficiency of BSB‐Me single‐crystal OLEDs with efficient exciton recombination and minimal Joule heat loss. In consequence, BSB‐Me single‐crystal OLEDs exhibit a maximum luminance of 50,170 cd/m2 and a peak EQE of 8.78%, which are better than DPA‐based devices. Furthermore, BSB‐Me single‐crystal HTLs with favorable interfacial properties enable large‐area OLEDs with uniform EL emission over the whole light‐emitting area of 1 mm × 1 mm. Interfacial properties of organic single‐crystal HTLs are investigated and verified to be vital to EL performances of single‐crystal OLEDs. High‐performance single‐crystal OLEDs can be realized with a peak EQE of 8.78% and a large functional area of up to 1 mm2. This work paves the way toward high‐performance organic single‐crystalline optoelectronic devices.

• Publisher: John Wiley & Sons, Inc
• Subject: Benzene / Boundary conditions / Contact angle / Crystal defects / electroluminescence / Excitons / Glass substrates / Heat loss / Interfacial properties / Light / OLEDs / organic single crystals / Simulation / Single crystals / single‐crystal HTLs / Software / Thin films / Transport properties / Wettability