Voltage-added n-p regenerative photoelectrochemical cells

As an alternative to conventional solid-state photovoltaic, regenerative photoelectrochemical (PEC) cells based on semiconductor/liquid junctions have attracted more and more attentions and attained competitive photoconversion efficiencies. However, most of the efficiency increases were achieved by various methods that can only increase the photocurrents, but not improve the photovoltage limits. Here, we show voltage-added regenerative PEC cell by combining n-Si photoanode with p-Si photocathode. By using CH₃CN as the solvent, LiClO₄ as the supporting electrolyte, and decamethylferrocenium/decamethylferrocene (Me₁₀Fc_+/0 ) as the redox couple, the n-p PEC cell can achieve an open-circuit photovoltage of 0.627 V, exceeding 0.480 V and 0.213 V for comprising n-PEC and p-PEC respectively. In addition, the PEC performances of single-crystal planar Si photoelectrodes and nanowire-array Si photoelectrodes prepared by electroless etching were compared. The wire-array electrodes showed an enhancement in photocurrent, but a slight decrease in phtovoltage. The high open-circuit voltage (>0.6 V) is also the highest ever reported voltage for Si-based PEC solar cells. This is paving the way for the development of a new generation of highly efficient PEC cells with high photovoltge and photocurrent.