Abstract
Here, we present a critical mini-review of the progression achieved and bottlenecks faced in the context of cuprous oxide (Cu2O)-based hybrid cells for photoelectrochemical water splitting, with a special focus on their integration with upconversion materials, photovoltaic systems and photoanodes for unbiased tandem devices.Cu2O photocathodes exhibit attractive properties that make them an appealing option, including a suitable bandgap, low-cost processing, and the potential for solarto-hydrogen efficiencies of up to 18% over a theoretical limit; however, their widespread application is limited by photocorrosion, low photocurrent, and poor light absorption.These systems demonstrate solutions to these challenges in solar-driven hydrogen generation, such as adding upconversion materials to increase the absorption spectrum and a tandem configuration for photovoltage and overall efficiency.It highlights the compact and modular features of this type of cell while reviewing its design principles, material strategies, performance metrics, and large-scale blending with renewable hydrogen production.