Hybrid photo-electrochemical and photo-voltaic cells (HPEV cells)

TL;DR

This paper introduces a multi-terminal hybrid PV and PEC system that enhances water splitting efficiency by allowing parallel power and fuel production, overcoming limitations of traditional series-connected tandem cells.

Contribution

The paper proposes and demonstrates a novel three-terminal HPEV cell design that improves efficiency and current matching in water splitting applications.

Findings

Devices produce electricity with minimal water splitting current reduction.

System surpasses current mismatch limits.

Increased overall efficiency of water splitting and power generation.

Abstract

The majority of photoelectrochemical (PEC) water splitting cells cannot drive the overall water splitting reactions without the assistance of an external power source. To provide added power, the cells are usually connected to photovoltaic (PV) devices in a tandem arrangement. This approach suffers from severe disadvantages since the PEC cell is connected in series to the PV cell and the overall current is typically limited by the saturation current of the PEC component. Thus, the operating point of the PV cell is often far from optimal and the overall system efficiency tends to be low. We propose a multi-terminal hybrid PV and PEC system (HPEV). As in tandem arrangements, the PEC cell is optically connected in series with the PV cell. However, a second back contact is used to extract the PV cell surplus current and allow parallel production of both electrical power and chemical fuel. Devices consisting of three-terminal silicon photovoltaic cells coupled to titanium dioxide water splitting layers are simulated and fabricated. The cells are shown to produce electricity with little reduction in the water splitting current, surpass the current mismatch limits, and increase the overall system efficiency.