Non-substituted 1,1',9,9'-bicarbazole and 3,3',6,6'-tetramesityl-1,1',9,9'-bicarbazole were synthesized through dimerization of carbazole derivatives and oxidative N-N bond formation reaction. Non-substituted 1,1',9,9'-bicarbazole formed a stacking packing structure in crystal. Both bicarbazoles were found to undergo acid-responsive electron-transfer disproportionation. The radical cation generated from the non-substituted 1,1',9,9'-bicarbazole was stable in solution under air at room temperature, even without protecting bulky substituents.