Blue thermally activated delayed fluorescent (TADF) emitters having 1-carbazolylcarbazole based donor moieties were developed to resolve the low quantum efficiency and large singlet–triplet energy splitting issues of the linker free TADF emitters. Investigation of the 1-carbazolylcarbazole derived donors as the donor units of two blue TADF emitters in comparison with 3-carbazolylcarbazole demonstrated that the 1-carbazolylcarbazole based donors increased the triplet energy, decreased the singlet–triplet energy gap, blue-shifted the emission color, and enhanced the quantum efficiency of the blue TADF devices.