Stabilized and Improved Photoelectrochemical Responses of Silicon Nanowires Modified with Ag@SiO2 Nanoparticles and Crystallized TiO2 Film

Semiconductor nanostructure photoelectrochemical (PEC) cells for sunlight conversion have the potential to supply continuous, low-cost, high-efficiency and carbon-free energy; however, in order to provide economically competitive energy, long-time stability and high-efficiency are requisite. In this work, the saturation photocurrent density (J(sat)) and stability of the silicon nanowires (SiNWs) in a PEC cell are significantly improved via surface modification with Ag@SiO2 nanoparticles and conformal TiO2 ultrathin film. Compared to the bare SiNWs, a 40% enhancement in J(sat), a cathodic shift of 0.8 V in the applied potential for J(sat), and over 10-h continuous operation with a high photocurrent density without decay are realized by using the properly modified SiNWs. Comparison of minority carrier lifetime indicates that the surface recombination of the modified SiNWs has been effectively suppressed. External quantum efficiency measurements reveal that the superstable and improved PEC responses of the modified SiNWs can be maintained for a broadband spectrum. This work provides an alternative route to the industrial applications for the semiconductor nanostructure PEC cells.