A team of researchers from Switzerland's École polytechnique fédérale de Lausanne (EPFL) and the US' Northwestern University have achieved more than 25% efficiency for inverted perovskite solar cells (PSC) using a new design.
The 25.3% lab-measured power-conversion efficiency was achieved with the introduction of a special molecule called 3-mercaptopropionic acid (3-MPA) into the cells' self-assembled monolayer (SAM) on textured substrates.
It is formed by a molecular layer of phosphonic acids substituted by carbazole that selectively extracts the positive charge carriers produced under illumination.
The team explains, "Adding 3-MPA enhances the contact between the perovskite material and the solar cell's textured substrate to improve performance and stability, allowing it to disassemble molecular carbazole clusters, and ensuring a more even distribution of the molecules in the self-assembled monolayer."
It helps avoid molecular agglomeration, which is a condition when molecules clump together instead of spreading out evenly, negatively impacting cell performance.
While leading to 25.3% efficiency, the inverted PSC maintained 95% of its peak performance even after being subjected to a temperature of 65°C and 50% relative humidity for over 1,000 hours. EPFL claims, "This level of stability, combined with such high efficiency, is unprecedented in the realm of PSCs."
Long-term stability is a challenge for the commercialization of perovskites even though these are known to generate high efficiency. EPFL and Northwestern University researchers claim their research addresses the hurdle by achieving both high efficiency and long-term stability.
Their research work has been published in the scientific journal Nature.