Low-Temperature Cross-Linkable Carbazole Derivatives: Their Structure−Property Relationship and Applications in Solution-Processed Organic Light-Emitting Diodes

High cross-linking temperatures often damage the under-layer during organic light-emitting diode (OLED) fabrication. In this study, we designed and synthesized a series of hole-transport materials featuring a carbazole/triphenylamine core and styrene terminal groups linked by flexible carbon chains. Crucially, the anchoring position significantly influences the thermodynamic characteristics. Substitutions at the 2- and 3-positions achieved a record-low cross-linking temperature of 110 °C, which is the lowest reported for purely thermally cross-linkable styrene derivatives. Furthermore, these materials exhibit a suitable highest occupied molecular orbital energy level (−5.21 eV), high triplet energy level (2.87 eV), and high hole mobility of 5.35 × 10 −4 cm 2 V −1 s −1 . Solution-processed multilayer OLEDs based on these materials demonstrate doubled device performance, delivering a maximum current efficiency of 77.9 cd A −1 and external quantum efficiency of 24.0%.