Pseudohalide induced tunable electronic and excitonic properties in two-dimensional single-layer perovskite for photovoltaics and photoelectronic applications

Two-dimensional (2D) layered organic-inorganic hybrid perovskites have attracted much more attention for some applications than their three-dimensional (3D) perovskite counterparts due to their promising thermal and moisture stabilities. In particular, the 2D perovskite devices have shown better promise for optoelectronic applications. However, tunability of optoelectronic properties is often demanded to improve the device performance. Herein, we adopt a newly method to tune the electronic properties of 2D perovskite by introducing pseudohalide into the structure. In this work, we designed a pseudohalide-substituted 2D perovskite by substituting the out-of-plane halide with pseudohalide and studied the electronic and excitonic properties of 2D-BA(2)MX(4) and 2D-BA(2)MX(2)Ps(2) (M-Ge2+, Sn2+, and Pb2+; X=I; Ps=NCO, NCS, OCN, SCN, SeCN). We revealed the dependence of electronic properties including band gaps, composition of band edges, bonding characteristics, work functions, effective masses, and exciton binding energies on different pseudohalides substituted in 2D perovskite. Our results indicate that the substitution of pseudohalide in 2D perovskites is energetically favorable and can significantly affect the bonding characteristics as well as the CBM and VBM that often play major role in determining their performance in optoelectronic devices. It is expected that the pseudohalide substitution will be helpful in developing more advanced optoelectronic device based on 2D perovskite by optimizing band alignment and promoting charge extraction. (C) 2019 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.