Revisiting Carbazole: Origin, Impurity, and Properties
Chengjian Chen, Kok Chan Chong, Yutong Pan, Guobin Qi, Shidang Xu, Bin Liu
Abstract
Photoluminescence quantum yield (PLQY) is one of the most important characteristics for organic luminescent materials. However, when carbazole prepared from the lab was compared to that from a commercial source, a remarkable change of PLQY was observed to vary from 37.1% to 69.8%. Taking 9-(4-bromobenzyl)-9H-carbazole (CzBBr) as an example of carbazole derivatives, the PLQYs of CzBBr synthesized from different origins of carbazole were varied from 16.0% to 91.1%. Our studies demonstrated that efficient radiative transition pathways were activated for commercial carbazole based luminescence, leading to a large enhancement in PLQY with fluorescence (from 16.0% to 54.4%) and phosphorescence (from <1% to 36.7%) for CzBBr. These results suggest that the origin of carbazole plays a very important role in determining the optical properties of carbazole derivatives, alerting us to carefully revisit carbazole and its derivatives, especially those with record-high efficiency.