New research from Northwestern University demonstrates how coated solar cells deliver a solar power conversion efficiency of 26 percent. This development could offer far higher performance for homes and businesses.
Currently, perovskite solar cells offer a lower-cost energy alternative to silicon solar cells, but they tend to degrade over time (a consequence of prolonged exposure to sunlight, extreme temperature fluctuations, moisture and humidity).
This has led to silicone dominating solar technology for many years. While silicon is durable and reliable, it is expensive to produce and is approaching its ceiling of efficiency.
Seen as a low-cost alternatives, perovskite solar cells typically use an ammonium-based coating layer to enhance efficiency. While effective, ammonium-based layers degrade under environmental stress, including heat and moisture.
To counter this, the researchers showed that by using amidinium ligands they could increase the degradation of passivation layers by ten times. Amidinium ligands are stable molecules that can interact with perovskite to provide long-lasting. The amidinium-based molecules comprise a central carbon atom bonded to two amino groups. Because their structure allows electrons to spread out evenly, amidinium molecules are more resilient under harsh conditions.
The amidinium-coated cells also tripled the cell’s T90 lifetime (defined as the time it takes for a cell’s efficiency to drop 90 percent of its initial value when exposed to harsh conditions). This was based on 1,100 hours of testing.
By chemically reinforcing the protective layers, the scientists significantly advanced the durability of the cells without compromising their efficiency. This introduces the steps towards practical, low-cost alternative to silicon-based photovoltaics.
The coating also led to a power conversion efficiency over 26 percent (this means the cells successfully converted 26.3 percent of their absorbed sunlight into electricity).
According to lead researcher Bin Chen: “The field has been working on the stability of perovskite solar cells for a long time. So far, most reports focus on improving the stability of the perovskite material itself, overlooking the protective layers. By improving the protective layer, we were able to enhance the solar cells’ overall performance.”
The research has been published in the journal Science. The paper is titled “Amidination of ligands for chemical and field-effect passivation stabilizes perovskite solar cells.”
