Realizing photoactive and thermodynamically stable all-inorganic perovskite solar cells (PSCs) remains a challenging task within halide perovskite photovoltaic (PV) research. Here, a dual strategy for realizing efficient inorganic mixed halide perovskite PV devices based on a terbium-doped solar absorber, that is, CsPb1-xTbxI2Br, is reported, which undertakes a bulk and surface passivation treatment in the form of CsPb1-xTbxI2Br quantum dots, to maintain a photoactive gamma-phase under ambient conditions and with significantly improved operational stability. Devices fabricated from these air-processed perovskite thin films exhibit an air-stable power conversion efficiency (PCE) that reaches 17.51% (small-area devices) with negligible hysteresis and maintains >90% of the initial efficiency when operating for 600 h under harsh environmental conditions, stemming from the combined effects of the dual-protection strategy. This approach is further examined within large-area PSC modules (19.8 cm(2) active area) to realize 10.94% PCE and >30 days ambient stability, as well as within low-bandgap gamma-CsPb0.95Tb0.05I2.5Br0.5 (E-g = 1.73 eV) materials, yielding 19.01% (18.43% certified) PCE.