Noble-Metal-Free Perovskite–BiVO₄ Tandem Device with Simple Preparation Method for Unassisted Solar Water Splitting

Unassisted solar water splitting can be realized by connecting a photovoltaic (PV) device in series with a photoelectrochemical cell (PEC). However, the complex fabrication methods and inevitable usage of noble metal have limited its development. In this work, we have constructed a wired tandem device with printable triple-mesoscopic perovskite solar cells and a BiVO₄ based PEC. Moreover, a noble-metal-free device was fabricated by using spin-coated amorphous MoS_x films as a cathode instead of Pt. In unit area, the different fabrication forms of perovskite solar cells were proved to have a huge influence for the overall performance of the tandem device, in which three-serial PV (PV3) based device showed the highest photocurrent density of ∼3.0 mA/cm² without external bias, and corresponding solar-to-hydrogen (STH) efficiency was 3.1%. The noble-metal-free tandem device was fabricated using spin-coating and screen-printing methods, representing an environmentally friendly and sustainable method to generate hydrogen fuel.