Three Ta-based compds. were successfully prepd. using a simple chem. synthesis. In dye-sensitized solar cell systems Ta3N5, TaOx, and Ta4C3 acted as counter electrode catalysts and demonstrated impressive catalytic activity and stability for I3- redn. The use of Ta-based counter electrodes resulted in a competitive photovoltaic performance, with high power conversion efficiencies of 5.03, 6.79, and 7.39% for Ta3N5, TaOx, and Ta4C3, resp., [equiv. to 66,4, 89.7, and 97.6% of the level obtained using Pt as a counter electrode (7.57%)]. By optimizing the prepn. process to reduce charge-transfer resistance and Nernst diffusion impedance, the development of high-performance Ta-based counter electrodes to replace Pt is expected for a wide range of applications including solar cells, fuel cells, biosensors, energy storage, and pollution control.