Photoelectrochemical Solar Energy Storage Cells

Although society’s electrical needs are largely continuous, clouds and darkness dictate that photovoltaic solar cells have an intermittent output. A photoelectrochemical solar cell (PEC) can generate not only electrical but also electrochemical energy and provide the basis for a system with an energy-storage component (PECS). Sufficientlyž energetic inQ1 solation incident on semiconductors can drive electrochemical oxidation/reduction and generate chemical, electrical, or electrochemical energy. Aspects include efficient dye-sensitized or direct solar to electrical energy conversion, photoetching, photoelectrochemical water-splitting, environmental cleanup, and solar energy storage cells. This chapter focuses on photoenergy storage concepts based on photoelectrochemical processes, but includes a necessary comparison to other methods proposed for the conversion and storage of solar energy. The PEC uses light to carry out a chemical reaction, converting light to chemical energy. This fundamental difference of the photovolatic solar cell’s (PV) solid–solid interface, and the PEC’s solid–liquid interface has several ramifications in cell function and application. Energetic constraints imposed by single band gap semiconductors have limited the demonstrated values of photoelectrochemical solar to electrical energy conversion efficiency to 16%, andmultiple band gap cells can lead to significantly higher conversion efficiencies [1, 2a,b]. Photoelectrochemical systems may facilitate not only solar to electrical energy conversion but has also led to investigations in photoelectrochemical synthesis, photoelectrochemical production of fuels, and photoelectrochemical detoxification of pollutants as discussed in other chapters in this volume.