Design of a functional rare earth oxide up-conversion layer for bulk silicon cells

Upconversion materials are typically tested using around 5mW of 1530nm laser illumination, which is equivalent to a solar concentration in excess of 1000 suns. An example of this can be found in where the NaYF:Er material is placed in proximity to a fully processed bifacial cell. Consequently the most obvious application for upconversion is to improve Si cells for use in low to medium concentrator photovoltaic (CPV) systems (2-300x). Previously we have demonstrated photocurrent via upconversion for a monolithically integrated rare earth oxide (REO) epitaxially grown on the front of a silicon test cell. The unique advantage arising from the integration of the REO directly onto the back of the silicon cell is that it can be processed using standard semiconductor techniques. This has the potential of lowering the cost of production because wafers could easily be scaled to 200mm diameter thereby accessing existing fabrication facilities. An increase in efficiency and a reduction in cost, presents an attractive opportunity for Si based photovoltaic (PV) and CPV.