Functional Charge-Transport Channels in Particle-Assembled Photoelectrodes: From Percolation to Interfacial Energetics

Particle-assembled semiconductor photoelectrodes can integrate high-quality powders derived from high-temperature or solution synthesis into devices, yet random and loose interparticle contacts often cause severe majority-carrier collection losses. This Perspective presents a unified framework coupling physical network construction with electronic design. Its physical construction requires percolation at low material loading without excessively covering reactive surfaces or pores, while electronic design demands carrier selectivity, energetic continuity, and high conductivity. We unify surface-derived layers, second-phase networks, and vertical scaffolds within this framework, shifting the focus from materials selection to conductive channel engineering. We identify controlled structural characterization, operando carrier-pathway probing, and long-term stability as current challenges, and propose future research strategies. We argue that such channel construction and electronic design could become a key pathway for particle-assembled photoelectrodes to advance from materials toward efficient devices.