Large-Grained Cu 2 BaSnS 4 Films for Photocathodes.

P-type compounds Cu2BaSnS4 (CBTS) are extremely attractive materials for photocathode application due to their suitable conduction and valence bands, earth-abundant sources, and environmental-friendly nature. Herein, an inexpensive and repro-ducible aqueous solution approach has been developed to synthesize CBTS films with single-crystalline grain 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 the bare Mo/CBTS film photocathodes under 100 mW·cm-2 illumination at 0 V versus RHE.