Wide range tuning of band gap energy of A3B2X9 perovskite-like halides

We report the structural, optical, and electrical properties of A(3)B(2)X(9) halides (where A = Cs, methylammonium (MA), formamidinium (FA), or ethylammonium; B = As, Sb, or Bi; X = Cl, Br, or I). Substitution results in tuning of lattice parameters involving crystal structure change, hence tuning of band gap energy, from similar to 1.9 to similar to 3.1 eV. Our results on the band gap energy, type, and crystal structure changes by A, B and X site substitution would give very useful information to develop wide band gap light-absorbers for diverse optoelectronic applications, including highly efficient and stable tandem solar cells. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.