A deep-blue crystalline organic light-emitting diode based on a solid-solution thin-film emitting layer

Owing to a highly ordered molecular arrangement, crystalline organic semiconductors have high carrier mobility, oriented alignment emitting dipoles, and high photon emission, which are beneficial for applications in organic light-emitting diodes (OLEDs). Blue, in particular, deep-blue OLEDs, have a significant impact on the color-gamut coverage and power consumption for the full-color display. However, desired deep-blue crystalline OLEDs (C-OLEDs) are still rare due to the difficulty in fabricating smooth crystalline thin films with horizontal dipole alignment and high photoluminescence quantum yield (PLQY). Organic solid solution (OSS) is a newly proposed promising method that can address these problems effectively, whose corresponding material systems are in urgent need of exploration and expansion. Herein, we report a deep-blue fluorescent C-OLED fabricated with a new crystalline OSS system by integrating crystalline matrix thin films with high-PLQY guest molecules. Our C-OLED demonstrates improved deep-blue emission with a maximum external quantum efficiency (EQE) of up to 5.3% with Commission Internationale de L'Eclairage (CIE) (0.15, 0.07). Moreover, C-OLED possesses much-improved performances compared to deep-blue amorphous OLEDs (A-OLEDs) (CIE y ≤ 0.08) in aspects of photon output capacity, driving voltage (4.6 V @1000 cd m −2 ), and series-resistance Joule-heat loss ratio (12.6%), confirming the feasibility of the OSS route for future development of OLEDs. Organic solid solution is a novel advantageous strategy for developing crystalline OLEDs. This work demonstrated its universality and extended the scope of material systems.