Wired and Wireless Photosynthetic Biohybrids: Design, Materials, and Mechanisms

Photosynthetic biohybrid systems (PBSs) integrate semiconductor light harvesters with microbial metabolism to enable solar-driven chemical synthesis, yet the chemical principles governing their performance remain dispersed across two distinct architectures: wired biohybrids, which rely on photoelectrode-microbe interfaces, and wireless systems, where microbes are photosensitized by colloidal or molecular catalysts. This review examines the materials chemistry, interfacial electron transfer mechanisms, and biological constraints that define each approach. We evaluate the stability and biocompatibility of semiconductor photoelectrodes, charge transfer pathways across abiotic/biotic interfaces, microbial community dynamics, and photoelectrochemical operational parameters central to wired systems. For wireless platforms, we analyze design rules for whole-cell photosensitization, including semiconductor selection, cellular uptake, redox coupling, and mechanistic probes of electron delivery. By comparing both architectures, we identify unifying chemical principles and key bottlenecks that limit efficiency, providing a framework for the predictive design of next-generation PBSs for sustainable solar-to-chemical conversion.