Novel Spiro Core-Based Hole Transport Materials for Stable Deep-Blue OLEDs with LT95 Over 420 h

Flexible, lightweight, and cost-effective organic light-emitting diodes (OLEDs) show great promise for use in displays and lighting applications. However, creating highly efficient and stable deep-blue OLEDs remains a challenge due to a lack of efficient functional materials, specifically hole transport materials (HTM). In this report, two new spiro-HTMs are introduced with fluorene (FBP-SFX) or dibenzofuran (DBF-SFX) peripheral substituents. This study finds that the DBF-SFX variant produces highly efficient deep-blue OLEDs with a narrow emission (full-width at half-maximum FWHM of 25 nm) and the highest external quantum efficiency (EQE) of 33.2% among the FBP-SFX (12.2%) and NPB (11.9%) variants. The superior performance of DBF-SFX is attributed to its deeper highest occupied molecular orbital level (HOMO) and small trap density, which results in reduced band-edge offset, lower turn-on voltages, and balanced charge carrier densities. Importantly, the blue fluorescence OLED with DBF-SFX displays exceptional device stability with LT95 over 420 h with an initial luminance of 1000 cd m(-2). This is due to the stronger bond dissociation energy (BDE) and suppressed Exciton-Polaron Annihilation (EPA) using the dibenzofuran substituent. This work demonstrates a new HTM design approach using a spiro-core architecture and dibenzofuran substituents to create efficient and long-lasting deep-blue OLEDs.