- The HZB research team increased the efficiency of perovskite-silicon tandem cells to 30.3% using a cesium chloride film.
- The solvent-free co-evaporation method addresses stability issues in perovskite cells, enhancing commercial viability.
- The new technique enables uniform perovskite film formation on textured silicon, reducing chemical reaction defects.
- Perovskite-silicon tandem cells are well-suited for clean energy needs in urban rooftops and high-energy industrial facilities.
Germany's Helmholtz-Zentrum Berlin (HZB) has announced a straightforward method to enhance the performance and commercial viability of high-efficiency "tandem" solar cells. The technique involves inserting an ultra-thin cesium chloride seed layer between sub-cells, improving the performance of monolithic perovskite-silicon tandem solar cells. Ultimately, the research team achieved a power conversion efficiency of 30.3% using a solvent-free co-evaporation process. The HZB team noted that this advancement effectively addresses long-standing industry challenges in mass production, paving the way for the industrial manufacturing of next-generation solar panels.
Standard silicon crystal layers feature nano-structures designed to optimize light absorption. However, this rough surface makes it difficult for organic self-assembled monolayers (SAMs), which serve as hole transport layers, to form uniformly. HZB scientists used the advanced infrared and X-ray instruments at the BESSY II synchrotron facility to closely observe the interface. They discovered that organic SAM molecules accumulated in the valleys of the textured silicon, leaving the peaks almost completely exposed. When researchers attempted to deposit the perovskite layer on top through evaporation, the uneven surface caused chemical reaction defects: harmful lead iodide formed in the gaps, significantly diminishing the cell's power generation capacity.
The Role of the Cesium Chloride Seed Layer
The introduction of the cesium chloride seed layer alters the microscopic landscape. This layer acts as a chemical foundation, smoothing out the underlying imperfections of the SAM layer and facilitating the smooth growth of perovskite crystals on the textured silicon surface. Lead author Dr. Viktor Škorjanc stated that this seed layer compensates for surface irregularities, aiding in the formation of a uniform co-evaporated perovskite film on textured silicon while avoiding defects caused by uneven coverage of the hole transport layer. Thanks to this, the resulting tandem solar cell achieved a conversion efficiency of 30.3%. According to the press release, this is an "extremely impressive figure" for perovskite cells prepared through evaporation.
Advantages of the Solvent-Free Process
This technology employs a solvent-free vacuum co-evaporation process, a commonly used method in the industry. The removal of chemical solvents from the process targets a major obstacle to the commercialization of perovskite solar cells: long-term material degradation and stability issues. The solvent-free process protects the underlying structure from degradation, producing more durable tandem cells and providing a feasible basis for the mass production of high-efficiency solar panels. Most record-breaking perovskite cells in the laboratory rely on spin-coating or wet chemical solution processing, methods that are difficult to scale up to large-area textured industrial-grade silicon wafers. In contrast, vacuum co-evaporation is already a standard process for manufacturing OLED screens and microelectronic products, significantly lowering the barrier to adoption by factories.
Future Application Prospects
HZB's perovskite solar cell evaporation team leader Dr. Marcel Roß stated, "This marks a genuine step forward in transforming laboratory record efficiencies into reliable, industrially manufacturable tandem solar technology." The HZB team's research is expected to provide the key technology for the industrial solar manufacturing sector to develop affordable next-generation solar panels. Perovskite-silicon tandem solar cells generate significantly more power per square foot than traditional silicon cells, making them particularly suitable for urban rooftops with limited space and high-energy industrial facilities aiming to maximize clean energy production.
Furthermore, perovskite is lightweight and can be designed to be semi-transparent, making it applicable for building-integrated photovoltaics (BIPV), allowing power generation technology to be directly integrated into building components such as skyscraper facades, glass windows, and skylights. The research findings have been published in the academic journal Joule.
Item Specification Solar Cell Type Monolithic Perovskite-Silicon Tandem Solar Cell Power Conversion Efficiency 30.3% Preparation Method Solvent-Free Vacuum Co-Evaporation Seed Layer Material Cesium Chloride (CsCl) Hole Transport Layer Organic Self-Assembled Monolayer (SAM) Analysis Equipment BESSY II Synchrotron Facility (Infrared and X-ray Instruments)
Breakthroughs and Application Potential of Perovskite Cell Technology
The HZB team's research demonstrates that the introduction of a cesium chloride film not only enhances the efficiency of perovskite-silicon tandem solar cells but also addresses long-standing stability issues in the industry. The solvent-free co-evaporation method paves the way for the commercialization of perovskite cells, making them particularly suitable for space-constrained urban environments and high-energy industrial facilities. As the technology matures, it is expected to find widespread application in areas such as building-integrated photovoltaics, further driving the development of clean energy.