γCbPhAP, a D-A dyad with γ-carboline as the D unit and 3-phenylacenaphtho[1,2- b ]pyrazine-8,9-dicarbonitrile as the A moiety and phosphorescence core, was designed and synthesized. The doping system of 1 wt% γCbPhAP in PMMA shows red ambient phosphorescence-dominated afterglow with long lifetime of 0.5 s and decent efficiency over 12%.