An international team of researchers has achieved a significant breakthrough in the efficiency of perovskite solar cells, demonstrating certified efficiencies exceeding 25.6%. This advancement came through a novel approach, which involves adjusting an ultrathin layer within the solar cells and employing a simple asymmetric molecule alongside a commonly used symmetric molecule, enhancing both performance and stability over time.
Research Method and Findings
Central to this innovation is the self-assembled monolayer (SAM), an essential component of inverted perovskite solar cells that facilitates the movement of positive charges. Researchers combined a symmetric SAM molecule, MeO-2PACz, with a simpler asymmetric molecule known as DTCA using a symmetry-breaking strategy. The approach aims to capture the advantages of molecular asymmetry without relying on more complex and expensive materials.
Corresponding author Tom Wu explained that the method effectively minimizes molecular self-aggregation, thereby improving surface coverage and the quality of the buried interface within the solar cells. Specifically, the team noted that the MeO-DTCA version achieved surface coverage of 82.4%, compared to just 60.6% for the MeO-2PACz alone.
Testing various formulations, the researchers found that a 4:1 ratio of MeO-2PACz to DTCA yielded the best results, leading to devices that reached certified efficiencies above 25.6%. The findings, which were published in Nature Communications, involved collaboration among scientists from China, Australia, the United Kingdom, South Korea, and Germany.
Further tests indicated that these combinations also suppressed undesirable chemical reactions caused by electrical stress and reduced non-radiative recombination losses. Consequently, they achieved a power conversion efficiency of 26.32% for a 0.012-square-inch solar cell and 25.34% for a larger, 0.155-square-inch cell. Additionally, an encapsulated device preserved 93% of its initial efficiency after 1,150 hours at maximum power output.
The research team has also developed a quantitative atomic force microscopy-infrared spectroscopy technique to measure the surface coverage of these molecular coatings at a nanoscale level. This breakthrough will help them explore further applications and combinations to improve solar cell technology.
Why It Matters
This research marks a significant step forward in the development of perovskite solar cells, which hold promise for enhancing the efficiency and reducing the costs of solar technology. Improved solar cell interfaces can lead to more reliable energy conversion, making renewable energy sources more accessible and efficient as demand for sustainable power continues to grow.
