Introduction: The Evolution of Thin-Film Photovoltaics
As the global energy landscape shifts toward renewable sources, the demand for high-efficiency, scalable, and flexible photovoltaic (PV) technologies has never been greater. While single-junction silicon solar cells are approaching their theoretical efficiency limits, tandem solar cells (TSCs) offer a way to break through these barriers. By stacking two different materials with complementary bandgaps, TSCs can harvest a broader spectrum of sunlight and minimize thermalization losses.
Among various tandem configurations, the monolithic (2-terminal) perovskite/Cu(In,Ga)Se2 (CIGS) tandem solar cell stands out as a premier all-thin-film solution. It combines the high performance of metal-halide perovskites with the proven durability and flexibility of CIGS. A recent study published in Nano-Micro Letters by a collaborative team from Helmholtz-Zentrum Berlin and University of Rome Tor Vergata provides a comprehensive roadmap for pushing the efficiency of these devices beyond 30% through advanced optoelectronic modelling.
The Current Benchmark: Certified 24.6% Efficiency
The starting point of this research is a state-of-the-art perovskite/CIGS tandem device with a certified power conversion efficiency (PCE) of 24.6%. Despite this high performance, significant losses remain. The researchers utilized a "physics-based modelling" approach to look inside the device layers and identify the exact locations where energy is lost.
By calibrating their models with experimental data—including current-voltage characteristics and external quantum efficiency (EQE)—the team identified two primary "efficiency killers":
The Synergetic Approach: Data-Driven and Optoelectronic Modelling
The researchers moved beyond simple trial-and-error experiments by integrating two powerful theoretical frameworks:
Roadmap to 35% Efficiency: Stepwise Optimization
Based on their models, the researchers proposed a three-step optimization strategy to reach the theoretical potential of this technology:
Real-World Impact: Annual Energy Yield
A unique aspect of this study is its consideration of real-world operating conditions. The performance of a solar cell varies throughout the day as the sun's spectrum changes. Using climate data from various locations, the researchers calculated the "Annual Energy Yield" (AEY). They found that perovskite/CIGS tandems are particularly effective because they maintain high efficiency even under diffuse light and varying temperatures, making them ideal for both rooftop installations and flexible applications in different geographic regions.
Conclusion and Future Outlook
The integration of experimental characterization with sophisticated data-driven modelling marks a significant advance in the field of tandem photovoltaics. By identifying the specific physical mechanisms that limit performance, the researchers have provided a clear engineering manual for the next generation of thin-film solar cells.
As fabrication techniques continue to improve, the move from 24% to 35% efficiency is no longer a distant dream but a planned progression. The perovskite/CIGS tandem solar cell is poised to become a cornerstone of the future fossil-free energy system, offering a combination of high power, low weight, and versatile form factors.
Nano-Micro Letters
News article
Assessment and Optimization of 2T Perovskite/CIGS Tandems via Data‑Driven and Optoelectronic Modelling
31-Mar-2026