Impact of triiodide ion incorporation on the absorption and photovoltaic efficiency of Bismuth-Based hybrid compounds

• The electronic and optical properties are obtained using first-principles. • The optical properties and efficiencies are split into different atomic species contributions. • The impact of triiodide ion on the optical properties and photovoltaic efficiency is analyzed. • The exchange of lead by Bi is evaluated. To determine whether the incorporation of triiodide ions into Bi-based hybrid compounds can serve as a substitute for iodoplumbates perovskites without diminishing photovoltaic efficiency, we analyzed the contributions of anions and triiodide ions to the absorption coefficients and conversion efficiencies across several compounds, both with and without triiodide ions. The electronic properties and absorption coefficients were obtained from first principles. To determine and quantify the key contributors to the optical gaps, the absorption coefficients and solar cell efficiencies are split as exact many-species expansions. The results reveal that while the triiodide contribution to the absorption coefficients and efficiencies is substantial, the primary distinction between compounds is attributed to the Bi-Bi interatomic distances. Nevertheless, the introduction of triiodide ions results in an increase in efficiency compared to the precursor compounds that lack triiodide ions.