Zintl-phase compounds ${AM}_2{\mathrm{Pn}}_2$ ($A=\mathrm{Ca}$, Sr, Ba; $M=\mathrm{Zn}$, Cd; $\mathrm{Pn}=\mathrm{N}$, P, As, Sb) have recently garnered growing attention in photovoltaic applications. Herein, we systematically investigate some key physical properties (quasiparticle band structures, exciton binding energies, and optical absorption coefficients) of these Zintl-phase materials as solar absorbers via first-principles calculations combining with the $G_0{W}_0$ approximation and Bethe-Salpeter equation. We demonstrate that the $G_0{W}_0@\mathrm{PBE}$ approach accurately predicts the band gaps of ${AM}_2{\mathrm{Pn}}_2$ compounds with $\mathrm{Pn}=\mathrm{P}$, As, and Sb, whereas $G_0{W}_0@\mathrm{LDA}+U$ achieves better consistency with experimental data for the ${AM}_2{\mathrm{N}}_2$ series. Calculated optical absorption spectra indicate that ${\mathrm{CaZn}}_2{\mathrm{P}}_2$ and ${\mathrm{SrZn}}_2{\mathrm{P}}_2$ exhibit relatively wide band gaps, rendering them promising candidates for top cells in tandem solar configurations. In contrast, ${A\mathrm{Cd}}_2{\mathrm{P}}_2$ ($A=\mathrm{Ca}$, Sr, Ba) and ${A\mathrm{Zn}}_2{\mathrm{N}}_2$ ($A=\mathrm{Ca}$, Sr, Ba) feature band gaps well suited for single-junction solar cells, while ${AM}_2{\mathrm{As}}_2$ and ${\mathrm{CaCd}}_2{\mathrm{Sb}}_2$, with narrower band gaps, are more suitable for bottom cells in tandem devices. Furthermore, the low exciton binding energies and small carrier effective masses of ${AM}_2{\mathrm{Pn}}_2$ compounds further underscore their potential for photovoltaic applications.

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• Band gap
• Excitons
• Photovoltaic absorbers
• Band structure methods
• Bethe-Salpeter equation
• GW method