In addition, CCO-1, CCO-2 and CCO-3 can also provide strong blue and deep-blue EL emissions at varied doping concentrations (Table ). For example, CCO-2 at 10 wt% doping concentration radiates strong deep-blue light peaking at 462 nm (CIEx,y = 0.14, 0.15) and attains the maximum ηext of 41.3%. At 50 wt% doping concentration, the EL peak moves to 470 nm (CIEx,y = 0.14, 0.19) and the maximum ηext remains as 41.6%. Notably, by increasing doping concentration from 10 to 50 wt%, the efficiency roll-offs decline gradually from 39.8% to 15.4% for CCO-1, 45.7% to 19.0% for CCO-2, and 46.4% to 16.1% for CCO-3. At high doping concentrations, kRISC is decreased, but kr is increased, which can effectively alleviate SSA (Supplementary Table ). Besides, taking CCO-2 for instance, the carrier mobility of 40 wt% doped film is more unbalanced than that of 20 wt% one, but the 40 wt% doped device has a much smaller efficiency rolloff. This result indicates that TPA should not be the dominant factor for the exciton loss (Supplementary Fig. ). Thus, the large efficiency roll-offs at low doping concentrations suggest that SSA is a main factor undermining efficiency stability when kRISC is large enough.