Stable and efficient multi-crystalline n+p silicon photocathode for H2 production with pyramid-like surface nanostructure and thin Al2O3 protective layer

Abstract

When a Si photocathode is used in a photoelectrochemical cell for H2 production, an open nanostructure capable of enhanced light absorption, low surface recombination, and being fully protected by thin protective layer is highly desirable. Here, we explored a highly stable and efficient multi-crystalline (mc) n+p silicon photocathode. A pyramid-like surface nanostructure on mc-Si wafer was fulfilled through a two-step metal-catalyzed chemical etching process, and then a n+p junction photocathode protected by a thin Al2O3 layer was constructed. The photocathode exhibits a high stability of continuous photoelectrochemical H2 production for above 100 h after a thin layer of Al2O3 is coated on its surface, and its energy conversion efficiency can be up to 6.8% after Pt loading, due to the lowered surface light reflection, increased surface area and minority carrier life time on the electrode surface.