Open Access

ARTICLE

Numerical Simulation of High-Performance Lead-Free BaZrS₃/CIGS Tandem Solar Cells

Jun Zhang, Jiayi Song, Wangjian Fu, Jiren Yuan^*

School of Physics and Materials Science, Nanchang University, Nanchang, China

* Corresponding Author: Jiren Yuan. Email:

Chalcogenide Letters 2026, 23(2), 2 https://doi.org/10.32604/cl.2026.077226

Received 04 December 2025; Accepted 03 February 2026; Issue published 28 February 2026

Abstract

Tandem solar cells employing lead-free perovskite materials offer a compelling pathway to simultaneously achieve high power conversion efficiency (PCE) and improved environmental sustainability. In this work, we present a comprehensive numerical simulation study of monolithic and mechanically stacked tandem solar cells based on the chalcogenide perovskite BaZrS₃ as the top subcell and Cu(In,Ga)Se₂ (CIGS) as the bottom subcell. For the four-terminal (4-T) configuration, a systematic optimization workflow was implemented, encompassing the thickness of absorber and carrier-transport layers, doping concentrations, and the introduction of a LiF anti-reflection coating. This approach led to a marked reduction in parasitic absorption and reflection losses, ultimately yielding a champion PCE of 34.7%. In the two-terminal (2-T) series-connected tandem, current matching was achieved by tuning the Ga content in the CIGS bottom absorber, which adjusts its bandgap and spectral response. Further co-optimization of doping profiles in the transport layers and the CIGS absorber resulted in a maximum PCE of 32.65%. Our analysis also highlights that the defect density within the BaZrS₃ layer is a critical performance governor; increasing trap densities severely degrade open-circuit voltage and fill factor, underscoring the importance of high-quality perovskite film synthesis. The results demonstrate the considerable potential of the eco-friendly BaZrS₃/CIGS tandem architecture for next-generation photovoltaics.

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