Recent Advances in Infrared‐to‐Visible Upconversion Photodetectors: From Multi‐Dimensional Innovations to Future Perspectives

Thin‐film infrared‐to‐visible upconversion photodetectors (UCDs) have emerged as a cost‐effective, pixel‐less paradigm for infrared (IR) visualization. This review first elucidates mainstream upconversion modalities, device configurations, and the physical principles of energy conversion, followed by a systematic definition of standardized performance metrics. Subsequently, we evaluate recent innovative strategies across four synergistic dimensions. For material frontiers, we trace the evolution of all‐inorganic, organic/inorganic hybrid, and all‐organic semiconductor systems regarding fabrication methodologies and optoelectronic performance. For structural evolution, a rigorous analysis of tandem architectures is conducted, specifically contrasting tandem light‐emitting diodes (LEDs) designed for efficiency multiplication against tandem photodetectors customized for achieving ultralow turn‐on voltages ( V on ) through photogenerated potential accumulation. Regarding mechanism innovations, we highlight performance and functionality enhancements facilitated by photomultiplication, optical microstructure, and color‐tunable emission. In terms of application paradigms, an overview of UCD deployment in bioimaging, medical monitoring, and wearable electronics is provided. Finally, we propose targeted strategic paths to address persistent challenges such as spectral response constraints, absence of multi‐dimensional information, and insufficient functional integration, thereby providing a comprehensive perspective for the future roadmap of intelligent, multi‐functional integrated UCDs.