Improving the Back Surface Field on an Amorphous Silicon Carbide Thin Film Photocathode for Solar Water Splitting
Paula Perez Rodriguez (TU Delft - Photovoltaic Materials and Devices)
Drialys Cardenas-Morcoso (Universitat Jaume I)
Ibadillah Digdaya (TU Delft - ChemE/Materials for Energy Conversion and Storage)
Andrea Mangel Mangel Raventos (TU Delft - Photovoltaic Materials and Devices)
Paul Procel Moya (TU Delft - Photovoltaic Materials and Devices)
O Isabella (TU Delft - Photovoltaic Materials and Devices)
Sixto Gimenez (Universitat Jaume I)
Miro Zeman (TU Delft - Electrical Sustainable Energy)
Wilson Smith (TU Delft - ChemE/Materials for Energy Conversion and Storage)
AHM Smets (TU Delft - Photovoltaic Materials and Devices)
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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 0.8V. 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 TiO2 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 150nm, after which the current saturates to 10mAcm-2 at 0V vs. the reversible hydrogen electrode in a 0.2m aqueous potassium hydrogen phthalate (KPH) electrolyte at pH4.