Silicon-based (Si-based) junctions have been widely investigated in recent years as photoelectrochemical (PEC) water splitting photoelectrodes, including buried junctions and metal–insulator–semiconductor (MIS) Schottky junctions. However, Si-based MIS photoelectrodes suffer from low performance for the PEC oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) because of the dilemma that a thin insulator cannot provide enough interfacial passivation while a thick insulator will block the transport of charge carriers. Another trade-off is the fact that the photovoltage extracted from the band offset between the metal and semiconductor will be counteracted by the parasitic light absorption of the metal layer, sacrificing the saturation photocurrent. This paper describes the design and realization of a bifacial passivation strategy for the metal/Si interface of an MIS photoelectrode, featuring a bi-layer stack consisting of amorphous silicon (a-Si) for passivating the silicon surface and a metal oxide (TiO₂) for passivating the metal surface. Upon the bifacial passivation of both a-Si and TiO₂, the minority carrier lifetime of the Si MIS photoanode was significantly improved from 18 to 2360 μs. Enabled by this extremely long minority carrier lifetime, it becomes possible to place the MIS junction on the back side of a Si substrate to construct an inverted-MIS (I-MIS) structure to eliminate the parasitic light absorption of traditional Si MIS photoelectrodes. The obtained photoelectrode exhibits an excellent onset potential of 0.85 V and 0.62 V vs. reversible hydrogen electrode (RHE) for the OER and HER, respectively. Eventually, unprecedented applied bias photon-to-current efficiencies (ABPE) of 3.91% and 12.66% were obtained by Si MIS and Si I-MIS, which are the highest among MIS-based photoanodes and photocathodes, with 30 h and 108 h stable operation. When pairing the Si I-MIS photocathode with a BiVO₄ photoanode to form a PEC membrane-free tandem cell, an unbiased solar-to-hydrogen conversion efficiency of 1.9% is achieved.

中文翻译：

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n硅金属-绝缘体-半导体光电极的双面钝化，可进行有效的氧气和氢气逸出反应

近年来，硅基（Si基）结已作为光电化学（PEC）水分解光电极进行了广泛研究，包括埋入结和金属-绝缘体-半导体（MIS）肖特基结。但是，Si基MIS光电电极在PEC析氧反应（OER）和析氢反应（HER）方面的性能很差，因为这样一个难题：薄的绝缘体无法提供足够的界面钝化，而厚的绝缘体会阻止电荷的传输运营商。另一个权衡的事实是，从金属和半导体之间的能带偏移中提取的光电压将被金属层的寄生光吸收所抵消，从而牺牲了饱和光电流。₂）钝化金属表面。通过a-Si和TiO ₂的双面钝化，Si MIS光阳极的少数载流子寿命从18μs显着提高到2360μs。通过这种极长的少数载流子寿命，可以将MIS结放置在Si衬底的背面上，以构建倒置MIS（I-MIS）结构，从而消除传统Si MIS光电电极的寄生光吸收。所获得的光电极表现出极好的起始电势，分别为0.85 V和0.62 V vs.。分别用于OER和HER的可逆氢电极（RHE）。最终，Si MIS和Si I-MIS获得了空前的应用偏置光子-电流效率（ABPE）分别为3.91％和12.66％，在基于MIS的光阳极和光电阴极中最高，稳定30 h和108 h手术。将Si I-MIS光电阴极与BiVO ₄光电阳极配对以形成无PEC膜串联电池时，可实现1.9％的无偏太阳能-氢转换效率。