What question did this study set out to answer?

Explore the impact of silver alloying on the properties and efficiency of (Ag,Cu)(In,Ga)S2 solar cells.

March 25, 2026Open Access

Silver‐Alloyed Wide‐Bandgap (Ag,Cu)(In,Ga)S 2 Thin‐Film Solar Cells With 15.5% Efficiency

YHYucheng HuUniversity of Cambridge EWEce WashbrookUniversity of Cambridge AOArivazhagan Valluvar OliUniversity of Luxembourg

Key Points

Explore the impact of silver alloying on the properties and efficiency of (Ag,Cu)(In,Ga)S2 solar cells.
Alloying Cu(In,Ga)S2 with silver to create (Ag,Cu)(In,Ga)S2 absorbers.
Analyzing compositional, structural, and optoelectronic properties of the alloyed material.
Measuring efficiency, open-circuit voltage, and carrier lifetime of the solar cells.
Achieved a power conversion efficiency of 15.5% with the (Ag,Cu)(In,Ga)S2 solar cell.
Increased open-circuit voltage of 948 mV compared to 821 mV for pure CIGS.
Demonstrated improved grain size, reduced porosity, and enhanced carrier lifetime, leading to suppressed bulk recombination.

Abstract

ABSTRACT Sulfide chalcopyrite Cu(In,Ga)S 2 (CIGS) is a wide‐bandgap semiconductor suitable for the top cell of a tandem solar device. Here, we demonstrate significant improvements in absorber quality by alloying with Ag to form (Ag,Cu)(In,Ga)S 2 (ACIGS) absorbers. We report the Ag alloying effect on compositional, structural, and optoelectronic properties of absorbers. We demonstrate suppressed bulk recombination and improved carrier lifetime in ACIGS, as a result of improved grain size, porosity reduction, and defect passivation. We also show that Ag alloying flattens the Ga gradient. Consideration of this impact of Ag will be necessary in future engineering of the Ga profile to maximize charge carrier collection and avoid interface recombination. Exploiting the beneficial effects of Ag alloying, we report a wide‐bandgap (1.58 eV) ACIGS solar cell with a high power conversion efficiency of 15.5% and a large open‐circuit voltage ( V OC ) of 948 mV, improving on the reference pure CIGS solar cell, with an 11.2% efficiency and an 821 mV V OC . Ag alloying is a useful route to further increase the efficiency of CIGS solar cells and future tandem devices.

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