First-Principles Study of Low-Dimensional Chalco-Halides for Photovoltaic Applications

Low-dimensional chalco-halides (LDCH) with general formula ABX (A=Bi,Sb, B=Se,S and X=Br,I) conform a new family of van-der-Waals materials with great promise for applications in critical energy fields like photocatalytic hydrogen production, thermoelectricity and sunlight energy conversion. However, due to their novelty and very recent synthesis, the physical and functional properties of LDCH have been little characterized thus far. We are interested in exploiting the potential of LDCH in state-of-the-art photovoltaic technologies able to compete with current single silicon junctions in terms of conversion efficiency and solar-cell costs. For this end, we present here an exploratory and comprehensive first-principles study based on density functional theory (DFT) calculations on the structural, vibrational and optoelectronic properties of LDCH. Our theoretical calculations for eight different compounds reveal, among other findings, energy band gaps within the range of 2.1-1.6 eV and remarkably large absorption coefficients of 580000 cm^-1, thus confirming the adequacy of LDCH for photovoltaic applications. The obtained theoretical results are compared with recent experimental measurements and complemented by photovoltaic device simulations.