Calculation of Energy Band Diagram of a Photoelectrochemical Water Splitting Cell

TL;DR

This paper introduces a physical model for PEC cells that accurately calculates energy band diagrams, including potential drops and band edge pinning effects, aiding the design of better water splitting semiconductors.

Contribution

It presents a comprehensive model that incorporates Helmholtz layer potential drops and charge transfer, improving upon previous models for PEC energy band calculations.

Findings

Model accurately predicts energy band positions and quasi-Fermi levels.

Calculated current-voltage curves match experimental data.

Model enhances understanding of semiconductor behavior in PEC water splitting.

Abstract

A physical model is presented for a semiconductor electrode of a photoelectrochemical (PEC) cell, accounting for the potential drop in the Helmholtz layer. Hence both band edge pinning and unpinning are naturally included in our description. The model is based on the continuity equations for charge carriers and direct charge transfer from the energy bands to the electrolyte. A quantitative calculation of the position of the energy bands and the variation of the quasi-Fermi levels in the semiconductor with respect to the water reduction and oxidation potentials is presented. Calculated current-voltage curves are compared with established analytical models and measurement. Our model calculations are suitable to enhance understanding and improve properties of semiconductors for photoelectrochemical water splitting.