Crystalline Silicon Photocathode with Tapered Microwire Arrays Achieving a High Current Density of 41.7 mA cm⁻2

Abstract

To design a high-efficiency crystalline silicon (c-Si) photocathode, the photovoltage and photocurrent generated by the device must be maximized because these factors directly affect the hydrogen evolution reaction (HER). In this study, a c-Si p-n junction is used to enhance the photovoltage of the c-Si photocathode, and a tapered microwire array structure is introduced to increase the photocurrent. When tapered microwire arrays are employed on the front surface of the c-Si photocathode, a current density of approximate to 41.7 mA cm(-2) is achieved at 0 V-RHE (reversible hydrogen electrode); this current density is the highest among all reported photocathodes including c-Si, approaching the theoretical maximum value for c-Si. Furthermore, a Ni foil/Pt catalyst is introduced on the opposite side of the incident light, simultaneously serving as an electrocatalyst to reduce side reactions in the HER and encapsulation layer to prevent c-Si from contacting the electrolyte. Thus, a stable device is developed using c-Si photoelectrochemical cells that have an efficiency exceeding 97% for >1000 h.