Over
the past few years, metal halide perovskite solar cells have
made significant advances. Currently, the single-junction perovskite
solar cells reach a conversion efficiency of 25.7%. Perovskite solar
cells with a wide band gap can also be used as top absorber layers
in multi-junction tandem solar cells. We examined the dynamical and
thermal stability, electronic structure, and optical features of In2PtX6 (X = Cl, Br, and I) perovskites, utilizing
first-principle calculations. The stability is predicted using phonon
dispersion spectrum and ab initio molecular dynamics
simulation and also through the convex hull approach. The lattice
constants and the optimized volume show an increasing trend with changing
halide ions. The band structures computed for In2PtCl6, In2PtBr6, and In2PtI6 indicate their semiconducting nature with band gap values
of 2.06, 2.01, and 1.35 eV, respectively. Halogens p and Pt d orbitals, respectively, play a prominent
role in the formation of states around valence band maximum and conduction
band minimum. The compounds, namely, In2PtBr6 and In2PtI6, exhibit high dielectric constants
and small carrier effective masses. Furthermore, we found that In2PtI6 reveals a maximum theoretical efficiency owing
to its optimum band gap and high optical absorption and is comparable
to MAPbI3 in the studied range. Our results suggest that
In2PtX6 (X = Cl, Br, and I) are suitable materials
for single-junction and top absorber layers in tandem solar cells.