Excitons in lead-halide perovskite nanocrystals from tight-binding GW/BSE approach

Lead-halide perovskite nanocrystals constitute a flourishing field of investigation due to their potential technological applications as tunable high-quantum-yield emitters[1]. Concerted research effort from both experimental and theoretical sides has helped in gaining a deeper understanding of the underlying parameters that play a role in determining the electronic and optical properties of these materials, such as the chemistry of the “A-site” cation or spin-orbit coupling[2]. Nevertheless, some fundamental quantities like the exciton binding energy and the multiplicity of the excited state are still a topic of debate. We addressed these issues with a tight-binding model parametrized on first-principle calculations and corrected within the GW approximation, and making use of the Bethe-Salpeter equation for the evaluation of the excitonic states[3]. This approach allows us to obtain the absorption spectra of methylammonium lead iodide nanocrystals of different dimensions and in different dielectric environments while retaining an atomic orbital description at each step.
[1]J.Shamsi et al., Chem. Rev., 2019, 119, 5,3296
[2]P.Sercel et al., Nano Lett., 2019, 19, 6, 4068
[3]Y.Cho and T. Berkelbach, J. Phys. Chem. Lett., 2019, 10, 6189