Improving the Back Surface Field on an Amorphous Silicon Carbide Thin‐Film Photocathode for Solar Water Splitting

Abstract

Amorphous silicon carbide (a-SiC:H) is a promising material for photoelectrochemical water splitting owing to its relatively small band-gap energy and high chemical and optoelectrical stability. This work studies the interplay between charge-carrier separation and collection, and their injection into the electrolyte, when modifying the semiconductor/electrolyte interface. By introducing an n-doped nanocrystaline silicon oxide layer into a p-doped/intrinsic a-SiC:H photocathode, the photovoltage and photocurrent of the device can be significantly improved, reaching values higher than 0.8 V. This results from enhancing the internal electric field of the photocathode, reducing the Shockley-Read-Hall recombination at the crucial interfaces because of better charge-carrier separation. In addition, the charge-carrier injection into the electrolyte is enhanced by introducing a TiO protective layer owing to better band alignment at the interface. Finally, the photocurrent was further enhanced by tuning the absorber layer thickness, arriving at a thickness of 150 nm, after which the current saturates to 10 mA cm at 0 V vs. the reversible hydrogen electrode in a 0.2 m aqueous potassium hydrogen phthalate (KPH) electrolyte at pH 4.

Hole‐Storage Enhanced a‐Si Photocathodes for Efficient Hydrogen Production

“…Compared with the a‐Si based photocathodes, [12, 13, 14b–d, 15, 36] a‐Si/Fh/Ni delivers the highest photocurrent density at 0 V vs. RHE and ABPE in alkaline electrolyte (Figure S20), even exceeding other copper‐based, [37] chalcogenide, [38] and CdTe [39] photocathodes. Furthermore, it is believed that the a‐Si/Fh/Ni would be an excellent photocathode to couple with photoanode for efficient overall water splitting in a stand‐alone dual‐photoelectrode PEC system.…”

BiVO4 Photoanode with NiV2O6 Back Contact Interfacial Layer for Improved Hole-Diffusion Length and Photoelectrochemical Water Oxidation Activity

“…For instance, modifying the amorphous silicon carbide with an amorphous TiO 2 front surface field (FSF) layer generates an internal electric field that improves the drift of photogenerated charge carriers and increases the operating photovoltage . Introducing a back surface field (BSF) layer such as n-doped nanocrystalline silicon oxide together with a TiO 2 FSF layer further improves the PEC performance of amorphous silicon carbide as a result of the enhanced internal electric field and charge-carrier separation efficiency . In fact, the BSF layer formation is extensively used to enhance the photovoltaic performance of solar cells.…”

“…23 Introducing a back surface field (BSF) layer such as n-doped nanocrystalline silicon oxide together with a TiO 2 FSF layer further improves the PEC performance of amorphous silicon carbide as a result of the enhanced internal electric field and charge-carrier separation efficiency. 24 In fact, the BSF layer formation is extensively used to enhance the photovoltaic performance of solar cells. The BSF layer at the interface with the base material (absorber layer) improves charge transport, reduces back surface recombination, and improves the collection of charge carriers.…”