The Institute of Photonic Sciences (ICFO) recently conducted a study in which researchers fabricated an optimal organic solar cell with both a high level of transparency and high power conversion efficiency. This is the latest step in creating cleaner, more affordable, and more ubiquitous renewable energy.
Solar panels have advanced rapidly in the 30 years they have been in existence. They are made of wafer-based silicon solar cells that convert solar radiation into electricity with 15% conversion efficiency. However, there are a few downsides. The panels have to be precisely aligned to receive direct sunlight and take up a tremendous amount of space. Even the most efficient solar panel is limited in its ability to absorb diffused light.
In contrast, organic photovoltaic (OPV) solar cells are lightweight, more flexible than their silicon-based counterparts, can adapt to curved surfaces, and are more sensitive to low light levels, including indirect sunlight. Between silicon-based solar cells and OPVs, OPVs have more advantages.
However, like all photovoltaic technology to date, OPV uses opaque devices to achieve maximum light-to-electricity conversion. If the OPVs are to be turned into transparent cells, the black metal electrode has to be thinned to the point of a few nanometers. This then limits the ability to collect sunlight.
Enter ICFO’s researchers. They have been able to implement a semi-transparent cell that incorporates a photonic crystal. Their cell can achieve a performance nearly equal to opaque cells. By adding an extra photonic crystal to the cell, ICFO’s scientists were able to increase the amount of infrared and ultraviolet light absorbed by the cell, reaching a 5.6% efficiency.
IFCO’s cells may lead to the creation of an extremely competitive product for Building-Integrated Photovoltaic (BIPV) technologies. The color of the cells can even be changed by modifying the layer configuration of the photonic crystal, allowing for a pleasing architectural look.