25.5% Efficiency For Perovskite Tandem Cell

• NREL researchers have achieved 25.5% efficiency for a tin-lead perovskite tandem solar cell
• They used 2 chemical compounds namely guanidinium thiocyanate and phenethylammonium iodide to help reduce defect density
• Researchers put the cell under an accelerated aging test in the lab and found it retained 80% of its maximum efficiency more than 62 days later

The National Renewable Energy Laboratory (NREL) under the US Department of Energy (DOE) has reported 25.5% efficiency for a tin-lead perovskite tandem solar cell, claiming that it retained 80% of its maximum efficiency after 1,500 hours of continuous operation.

It put together 2 layers of perovskites to achieve the efficiency level that didn't go down significantly after more than 62 days as it ascertained after an accelerated aging lab test.

Taking their research further from 2019 when some of the members of the NREL team reported an efficiency of 23.1% for tin-lead tandem perovskite cell with the addition of a chemical compound guanidinium thiocyanate, the team this time around also added phenethylammonium iodide.

"The improved tin-lead perovskite saw its carrier lifetime increase to about 9 microseconds. The combined additives also reduced the defect density associated with tin oxidation to a level unprecedented for tin-lead perovskites and similar to the values for lead-only perovskites," explains NREL. "The new cell also demonstrated an improvement in the voltage generated, at 2.1142 volts. In comparison, the best certified tandem device registered 2.048 volts."

Findings of this research have been published in science journal Nature Energy with the title Carrier control in the Sn-Pb narrow-bandgap perovskites via 2D cation engineering for all-perovskite tandem solar cells with improved efficiency and stability.

Back in October 2021, South Korean researchers from UNIST claimed the world's highest power conversion efficiency of 25.8% for a perovskite solar cell using organic HTL and Metal oxide ETL layers which the team said NREL certified as the highest confirmed efficiency of 25.5% (see 25.8% Perovskite Solar Cell Efficiency).

The NREL Perovskite tandem cell results follow on news this week by a team of researchers from Germany's Karlsruhe Institute of Technology (KIT) that have reported achieving 24.9% peak and 23.5% certified efficiency for a tandem solar cell comprising perovskite and copper indium diselenide (CIS) materials (see 24.9% Efficiency For Perovskite Tandem Cell).