<p>Inorganic lead-free halide perovskites (LFHPs) are emerging as eco-friendly alternatives to toxic Pb-based counterparts in photodetectors. This review establishes a ‘composition–dimension–interface triadic optimization framework’ to advance LFHPs. We first elucidate the stability rules of ABX₃ and derivatives (e.g., A₂B⁺B³⁺X₆ double perovskites), emphasizing the critical role of Bi³⁺ lone-pair electrons in defect tolerance. Next, dimensional engineering is explored, revealing 3DOM architectures as ideal platforms for light harvesting, while 0D nanocrystals enable ultrahigh quantum yields. Innovations in transport layers, particularly SnO₂ ETLs paired with Cs₂AgBiBr₆, achieve &gt;180-day stability. Despite detectivities up to 10¹³ Jones, LFHPs lag in carrier mobility (&lt;10 cm²&#xa0;V⁻¹&#xa0;s⁻¹) due to interfacial recombination. We propose a hierarchical roadmap: defect suppression via Rb⁺/Cu⁺ doping (short-term), scalable 2D/3D hybrid fabrication (mid-term), and perovskite/Si tandem cells (long-term). This work not only benchmarks the progress of LFHPs but also provides actionable strategies to bridge the efficiency gap with Pb-based devices.</p>