Boron Doping Modulates Carbazolocarbazoles with Color-Tunable Afterglow and Long-Lived Electroluminescence

Carbazolocarbazole (CCz) frameworks represent a promising class of afterglow-active emitters owing to their rigid helical π-systems. Here, we systematically investigate the effect of boron incorporation in a series of CCz derivatives (tOCCz, monoboron tBOCCz, and diboron tDBOCCz). Boron doping induces color-tunable hybrid afterglow combining thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence (RTP), with lifetimes exceeding 0.2 s and thermochromic shifts from green-yellow (300 K) to orange-red (77 K). Remarkably, an afterglow organic light-emitting diode (OLED) using tBOCCz as a single dopant achieves a low driving voltage of 2.8 V, record-high luminance of 22,021 cd m–2, a high external quantum efficiency of 5.0%, and ultralong electroluminescence (EL) visible for ∼2 s (lifetime 263 ms). Achieving high efficiency, high brightness, and extended EL duration together marks a benchmark for afterglow OLEDs. Overall, boron doping provides a versatile molecular strategy to realize color-tunable afterglow and durable EL for future responsive optoelectronics.