Novel Cross-Linkable Blue Light Emitting Material and Its High Stability OLEDs by Solution Process

• • The cross-linked blue emitters v-4CzBn and v-5CzBn achieve a singlet–triplet energy gap (ΔEST) ≤ 0.10 eV and a reverse intersystem crossing rate (kRISC) > 10^6 s−1, enabling efficient triplet harvesting in nondoped devices. • • Nondoped solution-processed OLEDs using S-4CzBn as the emitting layer deliver a maximum external quantum efficiency (EQE) of 12.01% and a maximum luminance of 11,141.15 cd m−2, demonstrating high electroluminescence performance. • • The devices exhibit an operational lifetime (T50) of 1375.66 hours at an initial luminance of 100 cd m−2, the longest reported for solution-processed OLEDs with cross-linked emitting layers, indicating superior stability. • • The thermal cross-linking reaction forms a three-dimensional covalent network that suppresses aggregation and crystallization, enhancing morphological stability and blocking moisture/oxygen ingress, which is critical for prolonged device operation.