According to a finding from KAUST researchers, adding a metal fluoride layer in multi-layered perovskite-silicon solar cells can delay charge recombination and improve performance.
Pair of solar cells that bind perovskite and silicon-based subcells in one gadget is likely to better harness and convert solar energy into electricity than their traditional single-junction silicon analogs at a lower cost.
However, the striking of sunlight of perovskite subcell leads the resulting pairs of elecrons and positively charged holes to tend to recombine at the interface between the electron-transport layer and perovskite.
Additionally, a difference between energy levels at the interface obstructs electron separation within the cell. This cumulatively lowers the maximum operating voltage that is available, or open-circuit voltage of the pair of cells and limits device performance.
Importantly, the performance issues can partially be solved. This involves introducing a lithium fluoride layer between electron-transport and the perovskite layer, which usually contains the electron-acceptor fullerene. On the downside, lithium salts liquefy readily and pass through surfaces, which make the devices unstable.
Meanwhile, all of these devices remain untested for the standard test protocols of the International Electrotechnical Commission, and thereby prompt to create an alternative, stated the lead author of the study.
The team of researchers systematically examined the possibility of other metal fluorides such as magnesium fluoride. This involved thermal evaporation of metal fluorides on the perovskite to create an thin uniform film with controlled thickness before including C60 and top contact constituents.
In fact, the interlayers are also highly stable and transparent to match inverted p-i-n solar cell specifications.
The magnesium fluoride interlayer effectively enabled electron extraction from the perovskite active layer while shifting C60 from the perovskite surface.