Kara Kearney1 2 Angus Rockett3 2 Elif Ertekin1 2

1, University of Illinois at Urbana-Champaign, Champaign-Urbana, Illinois, United States
2, International Institute for Carbon Neutral Energy Research, Fukuoka, , Japan
3, Colorado School of Mines, Golden, Colorado, United States

Photoelectrochemical water-splitting cells are typically composed of at least one semiconductor photoelectrode which is prone to deleterious degradation and/or oxidation. Various surface modifications are known for stabilizing semiconductor photoelectrodes, yet these stabilization techniques are often accompanied by a decrease in photoelectrode performance creating a roadblock for further improvements. In this work, we present a multiscale computational tool combining density functional theory (DFT) and finite-element device simulations. This integrated computational approach can be utilized to provide insight into charge transport across modified photoelectrodes and subsequently design functionalized photoelectrode for high efficiency photoelectrochemical water-splitting. To demonstrate the approach, we present how the tool has been used to analyze the performance of Si(111) photoelectrodes functionalized with mixed organic monolayers. DFT is used to calculate the changes in the electronic properties of the silicon induced by the organic functionalization. Then, the DFT results are used as input parameters for the finite-element device simulations. The device simulations are used to predict the efficiency of the operating photoelectrode based off calculations of the charge transfer behavior. This computational approach provides an inexpensive multiscale methodology that combines the angstom-scale results obtained using DFT with the micron-to-nanometer scale capability of device modeling.