Optimal Bandgap of Double Perovskite La-Substituted Bi_2FeCrO_6 for Solar Cells: an ab initio GGA+U Study

The ab initio generalized gradient approximation (GGA)+U study of multiferroic (La_0.5Bi_0.5)_2FeCrO_6 in pnma structure and ferri-magnetic order, including Hubbard corrections (U=4.1 eV) for transition metal/rare earth d-electrons with 20 atoms cell, shows optimum local magnetic moments of (Cr^3+, Fe^3+) equal to (-2.56, 4.14) \muB and an ideal spin-down band gap of 1.54 eV. Tuned-band gap La-substituted double oxide perovskites BFCO should exhibit enhanced visible-light absorption and carrier mobility, thus could be convenient light absorbers and then efficient alternatives to wide-gap chalcopyrite absorber-based solar cells failing to achieve highest power conversion efficiencies, and even compete with their metal-organic halide perovskites counterparts.