High‐Brightness Blue‐Emission Crystalline Thin‐Film OLEDs Based on Thick Solid‐Solution Emitting Layer

Abstract Organic light‐emitting diode (OLED) urgently needs to improve brightness to meet the demands from diverse light scenes in intelligent era. Owing to their high mobility and superior thermal stability, crystalline organic semiconductors possess intrinsic advantages than present amorphous thin‐film route to break through the bottleneck in OLED field and create high brightness devices. In this work, a deep‐blue crystalline thin‐film OLED (C‐OLED) is reported, which can achieve high brightness at low driving voltage (4817 cd m −2 @ 4 V). By integrating band‐like crystalline emitting layer and controllable p/n doping, C‐OLEDs demonstrate low turn‐on voltage, low series‐resistance joule‐heat loss ratio, and high power efficiency. This technological advancement, built on weak epitaxy growth (WEG) method and crystalline organic solid‐solutions (OSS) thin films, further validates the potential of the crystalline thin‐film approach in optimizing OLED performance, and provides a new engineering solution for the development of high‐performance organic light‐emitting devices.