High‐Efficiency Organic Single‐Crystal‐Based Light‐Emitting Diodes via Rational Crystal Packing

Abstract Organic single crystals (SCs) are promising candidates for high‐performance optoelectronic devices due to their high mobility of charge carriers and oriented alignment of transition dipole moments (TDMs). However, organic single‐crystal‐based light‐emitting diodes (SC‐based OLEDs) have until now struggled with poor device efficiency because of the lack of appropriate SC emitters; the integration of superior charge‐transport property and light‐emitting behavior into one single SC remains a great challenge. Here, two anthracene‐derivative SCs, 2,6‐di(6‐tert‐butylnaphthyl)anthracene (TBU‐DNA) and 2,6‐di(2‐naphthyl)anthracene (2,6‐DNA), are introduced into the construction of high‐efficiency SC‐based OLEDs. Through systematic investigations, rational crystal packing is revealed to play a critical role in tailoring the optoelectronic properties of SCs. Thanks to the slipped herringbone packing motif, TBU‐DNA SC is endowed with a higher photoluminescence quantum yield (PLQY) of 71.47%, an enhanced light‐outcoupling efficiency of 22.9%, and higher charge‐carrier mobility reaching up to 1.44 cm² V⁻¹ s⁻¹ along the crystal c‐axis, which are all responsible for better electroluminescence (EL) performances of TBU‐DNA SC‐based OLEDs. By optimizing the device structure with a hole‐blocking layer (HBL), the external quantum efficiency (EQE) of TBU‐DNA SC‐based OLEDs is approaching 3.46%, which is one of the highest EQE values for those OLEDs based on the SC emitting layer (EML) reported so far.