Electroless Excitation of Semiconductors through Semiconductor-liquid Interfaces

Electrochemistry of inorganic semiconductors has been studied extensively in the context of photoelectrocatalysis (e.g., water splitting, CO₂ reduction), corrosion and microfabrication technologies. On the other hand, little attention has been placed on studying the possibility of electroless excitation of semiconductors through semiconductor-liquid interfaces. We recently showed that electroless excitation takes place during metal-assisted chemical etching (MACE) of Si by using two different approaches. In the first approach,¹ a charge carrier collecting p-n junction structure coated with silver nanoparticles (AgNPs) was used to convert the chemical energy released during MACE to electricity using an electroless approach, i.e. without using any counter electrode, reaching a power density of 0.43 mW/cm². In the second approach,² we designed both n- and p-type Si photoconductors covered with AgNPs to probe their response to MACE. The experiments show that both n- and p-type photoconductors exhibit a strong response to MACE, seen as a significant increase of the currents through the photoconductors when exposed to the etching solution. All these experimental results imply that electroless excitation of Si takes place during MACE.<br/>In this presentation, we discuss the origin of these findings and the possibility to generalize the mechanisms of electroless excitation of semiconductors to other fuel-oxidizer systems. In particular, we discuss a framework for describing the thermodynamic and kinetic properties of the charge flow across the semiconductor-liquid interfaces during electroless excitation, aiming to establish the limits for the thermodynamic feasibility of the process.<br/>References:<br/>Li, S. et al.<i> J. Phys. Chem. Letters </i><b>2022</b>, 5648-5653.<br/>Li, S. et al. In Preparation, 2022.