Perovskite solar cells have been making headlines in recent years for their promise as a low-cost, lightweight, and highly efficient alternative to traditional solar panels.
But while they offer many advantages, there are still a couple of major problems holding them back from large-scale use.
One issue is their long-term stability, and the other is the fact that most high-performance perovskite solar cells rely on lead—a toxic metal that poses environmental and health concerns.
Researchers at HZB (Helmholtz-Zentrum Berlin) are now focusing on a more environmentally friendly option: solar cells made from tin perovskites.
Tin-based perovskites avoid the use of toxic lead and may offer better long-term stability.
They also work well in advanced solar cell designs like tandem and triple-junction cells, which stack multiple layers to capture more sunlight.
However, tin perovskites have not yet reached the same efficiency levels as their lead-based counterparts.
One area where researchers saw room for improvement was in the bottom contact layer of tin perovskite solar cells.
This layer is commonly made using a material called PEDOT:PSS, but it’s not ideal—it complicates the manufacturing process and leads to energy losses.
In lead-based perovskites, scientists have improved efficiency by replacing PEDOT:PSS with a much thinner and more elegant layer called a self-assembled monolayer, or SAM. This prompted the team to test SAMs in tin perovskites as well.
Initial efforts using a SAM compound called MeO-2PACz didn’t perform well in tin-based cells. Dr. Artem Musiienko and his team suspected the poor results were due to a bad fit between the SAM and the tin perovskite layer.
Computer simulations confirmed their suspicion: the molecular structure of MeO-2PACz didn’t align well with the tin perovskite, leading to energy loss.
So, the researchers searched for a better SAM compound—and found it in phenothiazine, a sulfur-based molecule known as Th-2EPT. Chemists at Kaunas University of Technology in Lithuania created the new compound, which forms a much better interface with the tin perovskite material.
Although the resulting perovskite crystals are smaller in size, their quality is high, and they lose much less energy.
The new solar cells with Th-2EPT achieved an efficiency of 8.2%, beating those made with PEDOT:PSS or MeO-2PACz. This result is a promising step toward developing efficient and lead-free tin perovskite solar cells.
According to the team, it proves that smart molecular design can make a real difference, bringing us closer to safer, greener solar technology.
Source: KSR.
