Efficient Near‐Infrared Fluorescence in Deuterated Host–Guest System for Near‐Infrared Organic Light‐Emitting Diodes

Abstract Near‐infrared organic light‐emitting diodes (NIR‐OLEDs) possess substantial potential for future valuable applications, such as a light source for sensing applications. However, the low photoluminescence quantum yield (PLQY) of NIR‐emitting molecules represents a significant impediment to these applications. In this study, the impact of the deuteration of both of host (mCP‐ d 20 : 1,3‐Dicarbazole‐benzene‐ d 20 ) and guest (BBT‐TPA‐ d 28 : 4,8‐bis[4‐( N , N ‐diphenylamino)phenyl]benzo[1,2‐c:4,5‐c']bis[1,2,5]thiadiazole‐ d 28 ) on NIR PL properties in the host–guest codeposited film is reported. The 1 wt%‐BBT‐TPA‐ d 28 :mCP‐ d 20 codeposited film exhibited PLQY of 15 ± 2% with an emission peak wavelength at ≈900 nm, which is about three times higher than that of the film composed of undeuterated molecules. Importantly, the deuteration of only the host or guest does not yield the PLQY up to 15%, underlining the importance of the deuteration of both host and guest molecules in suppressing nonradiative decay processes. The NIR‐OLED with the deuterated codeposited film as an emissive layer demonstrates a maximum external electroluminescence quantum efficiency of 2.3 ± 0.2%.