The lead contamination and long-term stability are the two important problems limiting the commercialization of organic–inorganic lead halide perovskites. In this study, through an innovative multi-scale simulation strategy based on the first-principle calculations coupling with drift-diffusion model and Monte Carlo method, a new discovery is shed on the vacancy-ordered double perovskite Cs₂TiI₆, a potential nontoxic and stable perovskite material for high-performance solar cell and α-particle detection. The excellent photon absorption character and ultrahigh carrier mobility (μ_n = 2.26×10⁴ cm²/Vs, μ_p = 7.38×10³ cm²/Vs) of Cs₂TiI₆ induce ultrahigh power conversion efficiency (PCE) for both single-junction solar cell (22.70%) and monolithic all-perovskite tandem solar cell (26.87%). Moreover, the outstanding device performance can be remained even in high energy charge particle detection (α-particle) with excellent charge collection efficiency (CCE = 99.2%) and mobility-lifetime product (μτ_h = 1×10^–3 cm²/V). Furthermore, to our surprise, the solar cell and α-particle detector based on Cs₂TiI₆ material are able to withstand ultrahigh fluence proton beam up to 10¹³ and 10¹⁵ p/cm² respectively, which strongly suggests that semiconductor devices based on Cs₂TiI₆ material are able to apply in the astrospace. The multi-scale simulation connecting from material to device reveals that Cs₂TiI₆ perovskite has the great potential for photovoltaic cells, α-particle detection and even their space application.