Exciton delocalization in layered perovskites from first principles

Optoelectronic properties of layered organic-inorganic halide perovskites can be tuned by leveraging their remarkable structural diversity [1]. In this work, we study the impact of several structural parameters of layered perovskites on their photophysics from first principles. We calculate the excited state properties of a series of layered perovskites with different structural features within the GW [2] and Bethe-Salpeter Equation (BSE) [3] frameworks (GW+BSE). We find that the key optoelectronic properties (i.e. band gaps, band structures, and optical spectra) depend strongly on the separation and alignment of the perovskite layers, and rationalize our findings from a tight binding perspective. We visualize the exciton with the electron-hole correlation function [4] and systematically link the structural features with the extent of exciton delocalization across the quasi-2D perovskites layers. Our study points to structural and chemical intuition by which we can tune the optoelectronic properties of layered perovskites by engineering changes to their crystal structure.

[1] Smith, M. D., et al. (2018). Annu. Rev. Mater. Res., 48, 111-136

[2] Hybertsen, M. S., & Louie, S. G. (1986). Phys. Rev. B 34, 5390

[3] Rohlfing, M., & Louie, S. G. (1998). Phys. Rev. Lett. 81, 2312

[4] Sharifzadeh, S., et al. (2013). J. Phys. Chem. Lett., 4, 13, 2197–2201