title: Efficiency limits for photoelectrochemical water-splitting.
abstract: Theoretical limiting efficiencies have a critical role in determining technological viability and expectations for device prototypes, as evidenced by the photovoltaics community's focus on detailed balance. However, due to their multicomponent nature, photoelectrochemical devices do not have an equivalent analogue to detailed balance, and reported theoretical efficiency limits vary depending on the assumptions made. Here we introduce a unified framework for photoelectrochemical device performance through which all previous limiting efficiencies can be understood and contextualized. Ideal and experimentally realistic limiting efficiencies are presented, and then generalized using five representative parameters-semiconductor absorption fraction, external radiative efficiency, series resistance, shunt resistance and catalytic exchange current density-to account for imperfect light absorption, charge transport and catalysis. Finally, we discuss the origin of deviations between the limits discussed herein and reported water-splitting efficiencies. This analysis provides insight into the primary factors that determine device performance and a powerful handle to improve device efficiency.
authors.affiliation: NG Next, 1 Space Park Drive, Redondo Beach, California 90278, USA.|Deparment of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA.|Division of Engineering and Applied Sciences, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA.|Joint Center for Artificial Photosynthesis, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA.
authors.forename: Katherine T
authors.initials: KT
authors.lastname: Fountaine
authors.affiliation: Division of Engineering and Applied Sciences, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA.|Joint Center for Artificial Photosynthesis, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA.
authors.forename: Hans Joachim
authors.initials: HJ
authors.lastname: Lewerenz
authors.affiliation: Division of Engineering and Applied Sciences, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA.|Joint Center for Artificial Photosynthesis, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA.
authors.forename: Harry A
authors.initials: HA
authors.lastname: Atwater