Large-Grained Cu2BaSnS4 Films for Photocathodes.

p-Type compounds Cu2BaSnS4 (CBTS) are extremely attractive materials for photocathode applications because of their suitable conduction and valence bands, earth-abundant sources, and environmental friendly nature. Herein, an inexpensive and reproducible aqueous solution approach has been developed to synthesize CBTS films with single-crystalline grains as large as micron scale. Because of the large crystalline grains, the as-grown CBTS films show excellent carrier mobility (1.29 cm2/V·s). Greater than 4 mA·cm-2 photocurrent density has been obtained in a neutral solution for bare Mo/CBTS film photocathodes under 100 mW·cm-2 illumination at 0 V versus reversible hydrogen electrode.