Surface Modification and doping of Semiconductor thin film: Effects on Band-Edge Positions, Short Circuit Current, photoelectrochemical efficiency and Surface Stability in Aqueous Photoelectrochemistry

الملخص: 

Many semiconductors have been extensively studied due to their suitable value band gap and the very high electron mobility. Despite of their wide applications in device manufacturing, the utilizations of semiconductors in PEC is limited by the following facts: they corrode with photocurrent (anodic corrosion).  Such degradation can be lowered by using suitable redox couples. This work aim to enhance the characteristics of semiconductors at the solid/liquid interface in photoelectrochemical systems.

Our hypothesis is that covering semiconductor surface with a polymer will affect the properties at the solid/liquid interface in the photoelectrochemical cells in different aspects: i) If the polymer contains positive charges then the semiconductor flat band potentials will be shifted toward more positive values.  ii) If the polymer contains a suitable redox couple it may behave as a catalyst for charge transfer across the semiconductor-liquid interface. This in turn will improve the short circuit current and lower the resistance.  iii) Furthermore, this redox couple will protect the semiconductor surface from degradation by catalyzing charge (hole) transfer to the electrolyte. The kinetics will therefore speed up hole transfer towards electrolytes rather than to semiconductor degradation.

Furthermore, annealing will strengthen the attachment of the polymer and the positive charges to the semiconductor surface. The resulting coated semiconductor will then be employed in photoelectrochemical cells.

Researchers use alternative systems for the J-V measurements of semiconductors in water. However, the water/K3[Fe(CN)6]/ K4[Fe(CN)6]/LiClO4 systems which are known to give poor results, in the dark and under illumination, will be intentionally employed in this work, so as to see if our modification technique is competent or not. If found to be satisfactory. it may then be employed for other semiconductors to obtain good candidates photocatalyst for light-driven water PEC cells.