<p>Vacancy-ordered double perovskites have emerged as lead-free alternatives, offering remarkable stability and compositional tunability for optoelectronic applications. In this study, we provide first-principles insights into their electronic properties, surface stability, and energy level alignment using a non-empirical dielectric-dependent hybrid functional. For representative family of the Cs<sub>2</sub>MX<sub>6</sub>, with M = Zr, Sn, Te, and X= Cl, Br, I, the predicted electronic band gaps are comparable to those obtained with the state-of-the-art GW method. We investigate the stability of these materials under simulated experimental conditions, considering both the rich and poor chemical potentials of their precursor salts. Our results indicate distinct regions of surface energy stability that favor CsX terminations. In contrast, MX<sub>4</sub> terminations show in-gap surface states, which can act as trap states and reduce carrier lifetime. Finally, based solely on the intrinsic absolute energy levels, we identify promising candidates as charge transport/injection layers for typical photovoltaic and light-emitting applications.</p>
