Solution Processing Silicon Heterojunction Photocathode for Efficient and Stable Hydrogen Production

Abstract

Efficient and stable photocathodes are crucial for the development of photoelectrochemical (PEC) water‐splitting devices. Silicon heterojunction (SHJ) solar cell is one of the most advanced photovoltaic cells. However, due to the instability of its outermost indium tin oxide (ITO) layers in the electrolyte, a protective layer needs to be introduced on its surface. Previously reported high‐quality protective layers almost all involved the use of expensive thin film manufacturing techniques such as atomic layer deposition (ALD). In this work, for the first time, a new strategy is proposed of modifying SHJ‐based photocathode with yttrium hydroxide (Y(OH)3) through two‐step solution methods to simultaneously improve the stability and activity. The optimized SHJ photocathode exhibits a high applied bias photon‐to‐current efficiency (ABPE) of 8.4% under simulated 100 mW cm−2 (1 Sun) with an AM 1.5G filter in 0.5 m KOH. Furthermore, the obtained SHJ photocathode demonstrates excellent stability of at least 110 h at 0.3 V versus RHE. In this work, combining facile direct current magnetron sputtering with a solution treatment technique provides a novel design strategy, which lowers the threshold for preparing high‐quality protective layer, and paves the way for developing economic, efficient, and stable SHJ‐based PEC devices.