Physical Chemistry

Enhancing Photovoltage of Silicon Photoanodes by a High Work-function Coordination Polymer

Authors

Abstract

A metal-insulator-semiconductor (MIS) structure based on an inhomogeneous junction has been recently proven to be highly efficient at photoelectrochemical (PEC) water oxidation. Engineering the surrounding layer of the MIS nanojunction is crucial to maximize the photovoltage. Specifically, for an n-type photoanode, a high work-function material is desired to create a large Schottky barrier that assists the hole transfer to oxidize water while blocking the electron transfer. We demonstrate the use of copper(I) thiocyanate (CuSCN), a transparent p-type coordination polymer semiconductor with a high work function, to surround the n-Si/SiOx/Cu nanojunctions, resulting in an increased effective barrier height from 0.71 to 1.03 eV. This phenomenon, known as the pinch-off effect, is also applied to improve the performance of the planar n-Si/SiOx/Cu electrode via a PEC dissolution method that creates an inhomogeneous surface covered with CuOx. The Cu/CuSCN nanojunction still shows superior performance due to the favorable energetics of CuSCN.

Version notes

The NRCT grant number is corrected to N42A650255 based on the updated information from the funding source.

Content

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Supplementary material

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Supporting information
Note S1: Experimental methods; Note S2: Verifying the formation of CuSCN layer; Note S3: Stability of Cu-modified Si photoanodes; Note S4: XPS characterization of as-sputtered and photodissoluted Cu; additional PEC characterizations; XPS spectra; Raman spectra; UV-Vis reflectance spectra; SEM images; OCP measurements; Kelvin probe measurements; photoelectron yield spectrum of the Au reference.