Abstract
InGaN-based nanowires (NWs) have been extensively studied for photoelectrochemical (PEC) water splitting devices owing to their tunable bandgap and good chemical stability. Here, we further investigated the influence of Si doping on the PEC performance of InGaN-based NW photoanodes. The Si dopant concentration was controlled by tuning the Si effusion cell temperature (TSi) during plasma-assisted molecular beam epitaxy growth and further estimated by Mott-Schottky electrochemical measurements. The highest Si dopant concentration of 2.1 × 1018 cm−3 was achieved at TSi = 1120 °C, and the concentration decreased with further increases in TSi. The flat-band potential was calculated and used to estimate the conduction and valence band edge potentials of the Si-doped InGaN-based NWs. The band edge potentials were found to seamlessly straddle the redox potentials of water splitting. The linear scan voltammetry results were consistent with the estimated carrier concentration. The InGaN-based NWs doped with Si at TSi = 1120 °C exhibited almost 9 times higher current density than that of the undoped sample and a stoichiometric evolution of hydrogen and oxygen gases. Our systematic findings suggest that the PEC performance can be significantly improved by optimizing the Si doping level of InGaN-based NW photoanodes.
Highlights
INTRODUCTIONInGaN-based nanowires (NWs) have attracted increasing interest for applications in photoelectrochemical (PEC) water splitting due to their chemical stability and tunable bandgap. By tuning the In composition during growth, the bandgap of InGaN can cover the entire solar spectrum while straddling the water splitting redox potentials. due to their three-dimensional (3D) geometry, NW-based photoelectrodes provide large surface-to-volume ratios that offer more benefits to the carrier separation process and increase the available surface area for electrochemical reactions. InGaN-based NWs are potential candidates for efficient PEC water splitting systems
InGaN-based nanowires (NWs) have attracted increasing interest for applications in photoelectrochemical (PEC) water splitting due to their chemical stability and tunable bandgap.1–6 By tuning the In composition during growth, the bandgap of InGaN can cover the entire solar spectrum1,7–9 while straddling the water splitting redox potentials.10,11 due to their three-dimensional (3D) geometry, NW-based photoelectrodes provide large surface-to-volume ratios that offer more benefits to the carrier separation process8,12 and increase the available surface area for electrochemical reactions.13 InGaN-based NWs are potential candidates for efficient PEC water splitting systems. the impact of the Si doping concentration on the PEC performance of InGaN-based NWs has been studied, it has been only reported for planar structures,14,18 which can be attributed to the lack of measuring techniques compatible with the NW geometry
Our systematic findings suggest that the PEC performance can be significantly improved by optimizing the Si doping level of InGaN-based NW photoanodes
Summary
InGaN-based nanowires (NWs) have attracted increasing interest for applications in photoelectrochemical (PEC) water splitting due to their chemical stability and tunable bandgap. By tuning the In composition during growth, the bandgap of InGaN can cover the entire solar spectrum while straddling the water splitting redox potentials. due to their three-dimensional (3D) geometry, NW-based photoelectrodes provide large surface-to-volume ratios that offer more benefits to the carrier separation process and increase the available surface area for electrochemical reactions. InGaN-based NWs are potential candidates for efficient PEC water splitting systems. By tuning the In composition during growth, the bandgap of InGaN can cover the entire solar spectrum while straddling the water splitting redox potentials.10,11 Due to their three-dimensional (3D) geometry, NW-based photoelectrodes provide large surface-to-volume ratios that offer more benefits to the carrier separation process and increase the available surface area for electrochemical reactions.. The impact of the Si doping concentration on the PEC performance of InGaN-based NWs has been studied, it has been only reported for planar structures, which can be attributed to the lack of measuring techniques compatible with the NW geometry. Complicated electron-beam lithography steps are necessary, which require high accuracy levels and can significantly increase the fabrication cost Compared with these techniques, PEC measurements based on electrochemical impedance analysis provide a new way to accurately estimate average dopant concentrations.. We found a close relationship between the optimization of the Si dopant concentration in n-type InGaN-based NW photoanodes and their PEC performance, which will be discussed in detail in PEC characteristics
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