Scientists achieve 25.4% efficiency in perovskite solar cells with enhanced stability using multivalent ligands

An international group of researchers has used multivalent amidinium ligands as an alternative to conventional monovalent ammonium ligands for passivation of perovskite films. When used in an inverted 2D/3D large area perovskite solar cell, the ligands contributed to achieving a cell power conversion efficiency of 25.4%, with the device maintaining over 95% of initial efficiency after 1,100 hours of continuous operation at 85 C under 1-sun testing.

The researchers focused on a controllable one-dimensional (1D) to two-dimensional (2D), 1D-to-2D, structural transition strategy to be applied to three-dimensional (3D) perovskite absorbers.

“The novelty of this work lies in the controllable transformation of low-dimensional (LD) passivation layers using amidinium ligand-induced 1D to 2D structures through precise modulation of intermolecular hydrogen bonding and π–π stacking,” Randi Azmi, co-corresponding author of the research, told pv magazine.

“Briefly, we demonstrated that choosing proper molecular ligand chemistry, or designing better ligands, considering their acidity and functional groups, to form more robust low-dimensional perovskite layers is critical for overcoming the fundamental instability issues of using conventional organic ammonium ligands,” said Azmi. “This structural control alters the dimensionality of the LD phase and simultaneously yields highly uniform and stable interfaces that sustain high performance even in large-area devices,” explained Azmi, noting that it is “a capability that had not been realized in earlier amidinium-based studies.”

By achieving a more detailed understanding of the mechanism, the researchers can now explore more advanced organic ligands, either commercially available ligands or new synthesized organic ligands that have the desired structures, according to Azmi.

Processing is reportedly uncomplicated. “We used a common solution process that everyone can follow to form in situ low-dimensional structures using spin-coating or dip-coating methods for large areas, where the molecular ligand design is important to enable the formation of uniform and controllable passivation layers,” Azmi said.

The technology was demonstrated in a 1.1 cm2 inverted 2D/3D large area perovskite solar cell device, which had a certified efficiency of 25.4%. The device maintained over 95% of initial efficiency after 1,100 hours of continuous operation at 85 C under 1-sun testing, which the researchers noted meets industrial requirements. In addition, a 4 cm x 4 cm mini module achieved an efficiency of 24.2%, according to the research.

Assessing the results, the researchers said that the work established “multivalency plus basicity-guided conformation of ligands as a general rule set for building robust 3D/2D heterojunctions,” highlighting that it offers a “practical passivation route” for durable, high-efficiency large-area perovskite optoelectronics.

“The amidinium ligands we’ve developed, and the new knowledge gained, allow the controlled growth of high-quality, stable perovskite layers. This could overcome one of the last major hurdles facing perovskite solar cell technology and ensure it lasts long enough for large-scale deployment,” co-corresponding author Thomas Anthopoulos said in a statement.

The research is detailed in “Multivalent ligands regulate dimensional engineering for inverted perovskite solar modules,” published in Science. Certification was provided by the National Institute of Metrology of China (NIM).

The study was led by researchers from University of Manchester and Chinese University of Hong Kong Shenzhen, along with King Abdullah University of Science and Technology (KAUST), Korea University, Shaanxi Normal University, National University of Singapore, and National Technical University of Athens.

From pv magazine Global

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