Star-shaped cross-linkable hole transport materials with high triplet energy and deep HOMO energy enable efficient solution-processed deep-blue TADF OLEDs
Solution-processed organic light-emitting diodes (OLEDs) face interlayer miscibility issues that degrade efficiency and lifetime. Cross-linkable hole transport materials (x-HTMs) with solvent resistance address this, but deep-blue OLEDs require high triplet energy (ET) and deep HOMO levels to confine excitons and facilitate hole injection. Two star-shaped x-HTMs, m-V-CzDPA and m-V-DPADPA, were designed with aromatic torsion structures yielding ET of 2.89 and 2.87 eV, respectively. Carrier diffusion coefficients of 0.54 and 0.44 cm2 s−1 and hole mobilities of 4.30×10−4 and 1.39×10−4 cm2 V−1 s−1 were measured. Solution-processed deep-blue TADF-OLEDs using x-m-CzDPA achieved maximum current efficiency of 5.25 cd A−1 and external quantum efficiency of 18.06% with CIE coordinates (0.162, 0.042), meeting BT.2020 standard (CIE y ≤ 0.046). This represents the first demonstration of x-HTMs enabling efficient deep-blue TADF-OLEDs via solution processing.