Chalcogenide-Silicon tandem PEC for CO2 reduction

Solar driven photoelectrohemical reduction of CO2 (CO2R) to valuable chemicals and fuels in artificial photosynthesis is of high importance for sustainable future and societal growth.

Among current PEC systems, electrolysis from PV cells using III-V semiconductors is promising but high material cost is a major limitation.

Integrated PV-PEC systems are desirable; however, they suffer from low performance due to insufficient solar spectrum utilization, carrier generation and transport losses, and poor catalysis.

An efficient and low-cost integrated system of a photocathode (PC) and photoanode (PA) is yet to be realized for simultaneous CO2R and oxidation of alcohol or water, respectively.

In this project, we propose a tandem architecture, including monolithic and wired connected design, comprising of (1.8 2.0 eV) bandgap Cu(In,Ga)S2 based top cell PC and silicon (1.1 eV) PA as bottom cell. The photovoltage of > 1.8 eV is targeted from CIGS-Si tandem system.

This will be accomplished by synthesizing high-quality CIGS optimized for interface recombination coupled with nanostructured and dual side doped Si.

The key aspect of the project is to couple the CO2R with the glycerol oxidation reaction which lowers the voltage requirement and makes it feasible for bias-free operation of CO2R and glycerol oxidation, thus producing valuable products like CO and formic acid at PC and PA respectively.

PC and PA will be individually optimized for high voltage, carrier selectivity, light management, high surface area catalysis and protected surfaces to avoid degradation. The design of the project allows to investigate device with electrical bias, similar to 3-terminal tandem PV device.

Separate PC and PA reaction chamber will make product separation easier with accurate estimation of the fuel production efficiency.

Applied bias, light intensity, light wavelength and catalyst coating layer will be varied and its relation to device performance and degradation will be established.