Hybrid organic-inorganic perovskite solar cells (PSCs) have recently become one of the mostefficient materials for photovoltaic applications [۱]. Formamidinium lead triiodide (FAPbI۳)perovskites possess high light absorption and stability, making them strong candidates for efficientsolar cells, yet they suffer from toxicity. The optoelectronic characteristics of environmentallyfriendly
alkaline earth metals substituted
FAPbI۳ (۱۰۰) surfaces, in various percentages, with PbI۶and PbI۵ terminations has been investigated using
density functional theory (DFT) as implementedin the Vienna ab initio simulation package [۲], (VASP ۵.۴.۴). We have created ۱۴ stable dopedstructures according to the Goldsmith tolerance factor [۳], in the form of FAPb۱-xAExI۳, (AE= Be,Mg, and Ca). Different terminations showed a negligible influence on the optical features, althoughtheir effect on the electronic properties is significant. Due to the conduction band (CB) shifting ofthe PbI۶ termination to the higher energies, an increase of about ۰.۳ eV in the bandgap of thistermination was obtained compared to that of PbI۵, and suitable bandgaps of ۱.۶۲۳ and ۱.۳۰۹ eVwere calculated for them, respectively. In doped systems, Mg and Ca substitution made broaderbandgaps, while two different decreasing and increasing trends on the bandgap of FAPb۰.۹۵Be۰.۰۵I۳and FAPb۰.۹۶Be۰.۰۴I۳ structures were observed. Promising optical activity such as appropriateextinction coefficient and light harvesting efficiency for plain and doped (۱۰۰) surfaces in thevisible and UV windows and also the high capacity of all structures to absorb more photons,especially in the near UV region for doped counterparts, altogether, indicate the capability of the(۱۰۰) surfaces for optoelectronic applications.