Broad-Absorbing Materials for Photodetectors: A Three-Factor Physical Model and Mechanism-Driven Design Strategies

• • The three-factor physical model (orbital, vibrational, spin) provides a unified framework for transition probability modulation, enabling cross-platform comparison of absorption broadening; this addresses the fragmentation that currently hinders systematic materials selection for broadband photodetectors. • • Inorganic materials achieve band structure modulation via alloying or doping, defect-induced states, and interfacial engineering in nanostructures or heterojunctions, while organic systems rely on molecular-level design such as bandgap narrowing, π-conjugation extension, spin-state manipulation, and charge-transfer engineering; these distinct mechanisms yield tunable absorption from UV to NIR, with specific examples including narrow-bandgap n-type polymers (e.g., Adv Mater 2020, 32: 2004183) and A-D-A'-D-A-type non-fused ring electron acceptors (Sci China Mater 2024, 68: 1–20). • • External-field enhancement mechanisms, particularly plasmonic resonance, contribute to spectral broadening and local-field enhancement, offering a route to boost photodetector performance beyond intrinsic material limits; this is critical for applications requiring high sensitivity and broad spectral coverage. • • The review identifies three core challenges for high-performance broadband optoelectronic systems and proposes mechanism-driven design strategies, providing an instructive outlook for future advancements; this is industrially relevant for multispectral imaging arrays, solar energy conversion, and integrated optoelectronics where spectral coverage and multifunctionality are paramount.