A rhodium(III)-catalyzed indole-directed aryl C–H bond carbenoid insertion cascade of 2-arylindoles with diazo compounds has been developed. This method provides a rapid access to 1,2-benzocarbazoles and isoquinoline-based polycyclic heteroaromatics with a broad range of functional group tolerance. The primary evaluation of the photoluminescence property of the novel extended π-systems indicated that these heteroarenes could be potentially used in the field of optoelectronic materials.