HZB Achieves 30.3% Efficiency in Perovskite-Silicon Tandem Solar Cells Using Solvent-Free Co-Evaporation with Ultra-Thin CsCl Layer

August 30, 2026

XenoSpectrum Germany

Overview

Germany’s Helmholtz-Zentrum Berlin (HZB) has achieved a 30.3% (certified 29.7%) power conversion efficiency for perovskite-silicon tandem solar cells, employing a solvent-free co-evaporation method and an ultra-thin cesium chloride (CsCl) seed layer. While not surpassing the current world record of 35.5%, this represents an excellent figure for deposition-based manufacturing, contributing to uniform perovskite growth and suppressing interface impurities. This breakthrough paves the way for more sustainable and scalable production.

In Depth

Key Findings

Researchers at Germany’s Helmholtz-Zentrum Berlin (HZB) have achieved a new breakthrough in perovskite-silicon tandem solar cells. By implementing an innovative solvent-free co-evaporation method and introducing an ultra-thin cesium chloride (CsCl) seed layer, measuring just a few nanometers, they reached a power conversion efficiency of 30.3% (certified 29.7%). Although this does not surpass the world record of 35.5% held by China’s LONGi, it represents an exceptionally high value for deposition-based manufacturing methods, in contrast to solution processes, indicating a significant advance in perovskite layer quality and the sustainability of the manufacturing process.

Technical Details

The key to this achievement lies in the combination of the solvent-free ‘co-evaporation method’ and the introduction of the ‘CsCl seed layer.’ Traditional solution processes for forming perovskite layers often rely on organic solvents, presenting challenges related to manufacturing complexity, environmental impact, and layer uniformity. The co-evaporation method overcomes these issues, making it suitable for industrial-scale production. Furthermore, the research team utilized an ultra-thin CsCl seed layer to control the growth of the perovskite layer. This CsCl layer performs two critical functions:

Promoting Uniform Perovskite Growth: The formation of the CsCl layer on the substrate facilitates uniform nucleation of subsequent perovskite crystals, leading to the formation of high-quality, defect-free perovskite layers.
Suppressing Undesirable Lead Iodide Formation at the Interface: It effectively inhibits the formation of unwanted byproducts, such as lead iodide, which can occur at the interface between the perovskite and other layers. This prevents device performance degradation and enhances stability.

These technological approaches have significantly improved the efficiency of perovskite-silicon tandem solar cells, marking a major step towards their practical application.

Background & Context

Perovskite solar cells are globally recognized as a next-generation renewable energy technology due to their potential to achieve efficiencies that exceed the theoretical limits of conventional silicon solar cells. Tandem structures, particularly those combining perovskite with existing silicon solar cells, are highly anticipated for their ability to efficiently utilize a broader range of the solar spectrum, with expectations of achieving efficiencies over 30%. HZB’s achievement is significant because it demonstrates high efficiency using a scalable vapor deposition method, which provides a clear pathway for mass production and cost reduction. The solvent-free process is also highly attractive to industry due to its environmental friendliness and enhanced safety in manufacturing environments.

Strategic Significance & Outlook

This achievement of 30.3% efficiency will provide strong momentum for the commercialization of perovskite-silicon tandem solar cells. The solvent-free manufacturing process, in particular, will be a highly attractive option amid increasing environmental regulations and demands for sustainable production. As HZB’s technology further develops and production scales expand, it is expected that high-efficiency, low-environmental-impact next-generation solar cells will play a crucial role in the global energy market. This represents an indispensable technological innovation for accelerating efforts against global warming and transitioning to clean energy.

Source: https://xenospectrum.com/en/hzb-perovskite-tandem-vapor-deposition/

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