Scientists from Saudi Arabia’s King Abdullah University of Science and Technology (KAUST) have reported the results of a one-year outdoor test for a tandem perovskite-silicon solar cell they developed in 2020. They have found that the device retained more than 80% of its initial efficiency during the testing period between April 2021 and April 2022.
The team's results are actual outdoor measurement over months and months, rather than testing done in a lab-controlled environment. The team is still conducting tests, aiming to focus on stability and reach at least a two-decade operation goal.
In the recent report, the research group stressed the importance of robust encapsulation to minimize encapsulation-related failures. The scientists soldered two metal wires on both sides of the cell to extend the electrode contacts. They then encapsulated the device between two layers of thermoplastic polyurethane (TPU) and glass before module lamination.
They deployed the tandem solar cell at a tilt angle of 25 degrees and a southern orientation. They then tested it at a KAUST testing facility in Saudi Arabia, with a global horizontal irradiance (GHI) of approximately 2,240 kWh per square meter.
“The combination of high irradiance, high temperature, and high relative humidity makes this given location a challenging environment for perovskite-based solar cells but a most relevant location to study the outdoor resilience of PV technologies,” said the scientists.
The tandem device's fill factor remained above 78% for the first four months and then gradually decreased from August until December to around 72%. At the end of the first year of operation, it remained above 70%.
“Knowing that the fill factor is the parameter that is most prone to degrade outdoors, the results are promising toward achieving stable tandem technology,” the researchers said.
They noted that by the end of April 2021, the cell was still able to retain more than 80% of its initial efficiency.
“It is a big jump for us in terms of outdoor stability but it is clear that we have room for improvement,” researcher Maxime Babics said. “It is also important to mention that this generation of tandems was developed in our lab at the end of 2020 and I am confident to say that the new generation of the tandem that we are fabricating at the moment could provide better results.”
