PVTIME – Tongwei Co., Ltd.’s PV Technology Centre has announced a significant breakthrough in perovskite-silicon tandem solar cells. The new cell design has achieved a conversion efficiency of 31.4%. This result has been formally verified by the National Institute of Metrology, Testing Technology (NIMTT) and the Fujian Institute of Metrology (FJIM), and outperforms the 29.43% efficiency achieved by control groups using traditional annealing processes. This breakthrough sets a new industry record and marks a critical step forward in China’s efforts to commercialise next-generation, high-efficiency photovoltaic cell technology.
The tandem cell features a wide-bandgap perovskite (1.73 eV) top cell paired with a full-textured silicon heterojunction (SHJ) bottom cell, forming a double-terminal stacked device. A key innovation behind this development is the team’s creation of a low-temperature “sequential annealing” fabrication process. Conducted under normal ambient conditions, this process involves the precise regulation of annealing temperatures and timing phases, significantly enhancing the coverage and crystallisation quality of perovskite films on textured silicon surfaces. This delivers low-defect, highly uniform conformal growth, which directly improves the cell’s performance and stability. Corresponding author Hu Yuchao explains that the entire process operates at 100–150 °C and takes no longer than 30 minutes, offering strong compatibility with existing SHJ production lines and clear potential for commercial use.
For many years, the industry has faced significant challenges in integrating wide-bandgap perovskites into commercial silicon cells, particularly with regard to the impact of moist and high-temperature conditions on film crystallisation and quality. To address this issue, the Tongwei team conducted research into phase transition mechanisms and crystallisation kinetics, developing a ‘sequential crystallisation strategy’ that enables precise control over organic halide diffusion and perovskite recrystallisation. This approach has led to the successful production of high-performance functional layers. The cell has ultimately achieved an open-circuit voltage of 1.905 V, a fill factor of 81.20%, and a short-circuit current of 20.30 mA/cm², all of which meet internationally leading standards.
In terms of device structure, the p-i-n perovskite subcell uses a composite hole transport layer of nickel oxide (NiOx) and 2PACz, with ethylenediammonium iodide (EDAI₂) introduced for interface passivation. The electron transport layer uses a C60/SnOx stacked structure. These material and process choices not only boost efficiency, but also improve the device’s weather resistance and manufacturability, striking a balance between cutting-edge performance and engineering practicality.
Tongwei has outlined a clear roadmap to transition the technology from laboratory research to mass production. Since setting up its Third Laboratory in 2022, the company has aligned its research and development efforts to ensure compatibility with existing SHJ production lines. This year, Tongwei plans to build a megawatt-scale pilot line to focus on overcoming key technical challenges such as fabricating cells on a large scale, laser scribing, low-temperature metallisation, and ensuring the long-term reliability of modules. These actions lay a solid foundation for the practical deployment of the technology.
As photovoltaic technology evolves from P-type to N-type and now to tandem structures, Tongwei’s efficiency breakthrough represents more than just a numerical milestone. It demonstrates the gradual shift of Chinese PV enterprises from following international technology trends to leading in certain areas. Against the backdrop of the global energy transition and China’s “dual carbon” goals, technologies that combine high efficiency, low cost, and scalability are breathing new life into the PV industry, while also strengthening China’s influence in the global competition for new energy technologies.
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