An international research team has developed a new two-dimensional perovskite interlayer based on a co-crystal engineering strategy for more robust perovskite films. It demonstrated improved performance in small-area perovskite solar cells and, in a 48 cm2 module, contributed to maintaining 95% of initial efficiency after 5,000 hours.
An international research team has achieved record stability of perovskite solar panels under light, heat and UV loads with an industry-compatible chemistry-driven passivation technology. It is striking that a demonstration module of 48 cm2 retained approximately 95% of the initial efficiency after 5,000 hours of sunlight at 1 exposure and a maximum power point (MPP).
“The main novelty of this work is the introduction of a co-crystal engineering strategy for two-dimensional (2D) perovskites based on neutral molecules, instead of conventional ionic bulky cations,” said corresponding author Narges Yaghoobi Nia. pv magazine, adding that the study showed that neutral triazine-based molecules known as benzoguanamine (BGA) can act as “coformers to assemble into a stoichiometric 2D perovskite cocrystal phase through intermolecular interactions rather than ion exchange.”
The researchers determined that BGA selectively passivated both halide and cationic vacancies in perovskite composite thin films by “forming strong Lewis adducts and intermolecular bonds,” and operated as a multifunctional agent.
“These BGA-based 2D perovskite films effectively block ion migration and the outgassing of volatile MA+ cations under long-term ambient illumination,” the researchers said, adding that the stable 2D perovskite phase did not alter the native 3D perovskite stoichiometry.
According to Yaghoobi Nia, it was also new to use non-polar, industry-compatible solvents to prevent damage to the 3D layer.
A demonstration of the treated films in optimized perovskite solar cells resulted in efficiency retention of more than 95% after 5,000 hours of immersion in 1 sunlight and MPP conditions. In thermal stress testing, the target device had an efficiency retention of over 91% after 5,000 hours at 85 C and an efficiency retention of over 98% under 1,000 hours of continuous UV exposure and MPP tracking under atmospheric conditions.
The researchers also fabricated modules with an active area of up to 48 cm² with an energy conversion efficiency of 18.5% and stability levels beyond commercial IEC/ISOS requirements. Solar cells with a small surface area had an efficiency of 23.4%.
“Our cocrystal engineering method shows a clear improvement in both efficiency and stability compared to previously published results,” the researchers said. “Together, these developments directly address one of the last major barriers to perovskite commercialization: long-term module stability under realistic operating conditions,” says Yaghoobi Nia.
In terms of manufacturability, the co-crystal engineering process is designed to be compatible with existing perovskite production workflows.
“From a process perspective, it is a single additional deposition step on top of a standard 3D perovskite layer,” explains Yaghoobi Nia, adding that it does not require complex synthesis, high-temperature processing, vacuum steps or new capital-intensive tools. “This lowers the barrier for technology transfer to existing PV production lines,” she noted.
The 2D cocrystal layer is formed by deposition of a solution from a nonpolar solvent, followed by mild thermal annealing. “Importantly, the complexity is chemical rather than technological in nature. The innovation lies in molecular design and interfacial chemistry, and not in added production steps. This makes the approach very attractive for scale-up and industrial adoption,” emphasizes Yaghoobi Nia.
The research was led by a team from Iritaly Trading Company and École Polytechnique Fédérale de Lausanne (EPFL), joined by researchers from the University of Rome Tor Vergata, Institute of Structure of Matter, Argonne National Laboratory, Italy-based Greatcell Solar.
The researchers assessed the work with BGA as a “groundbreaking compound for realizing unique cocrystal low-dimensional perovskite phases using nonpolar solvents, leading to highly efficient and stable perovskite devices.”
It is described in detail in “Co-crystal engineering of a two-dimensional perovskite phase for perovskite solar panels with improved efficiency and stability”, published in Nature energy.
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