“…6 These properties, especially the broken out-of-plane symmetry and ferroelectricity, lead to an enlarged light absorption, even in the infrared region. 7 The investigation of 2D Janus structures (compounds with a biphasic or asymmetric structures), [8][9][10][11][12] including transition-metal dichalcogenides, such as Ga 2 SeTe, Ga 2 STe, and Ga 2 SSe monolayers, 13,14 showed that due to their unique structural characteristics, a built-in electric field results from the difference in the electrostatic potential between the two surfaces of the 2D materials. Thanks to this characteristic, the solar to hydrogen conversion efficiency of Janus Pd 4 S 3 Se 3 reaches up to 30.1% overcoming the theoretical efficiency limit, 18%, of popular 2D MoS 2 .…”