Solar photovoltaic power generation represents a clean and renewable energy solution. Recently, researchers from the Key Laboratory of Microsystem Technology at the Shanghai Institute of Microsystems and Information Technology, led by Dr. Liu Zhengxin, collaborated with Professor Liu Mingzhen from the University of Electronic Science and Technology to develop a perovskite/silicon heterojunction (SHJ) tandem solar cell with an impressive conversion efficiency nearing 29%. This achievement marks the highest efficiency for industrialized all-textured SHJ solar cells to date. The study was published in *Advanced Materials* under the title "Fully Textured, Production-line Compatible Monolithic Perovskite/Silicon Tandem Solar Cells Approaching 29% Efficiency."
Currently, the peak conversion efficiencies for single-junction silicon SHJ solar cells and perovskite solar cells stand at 26.5% and 25.7%, respectively. Theoretically, perovskite tandem solar cells built on high-efficiency SHJ solar cells could exceed 40.0% efficiency, making this technology widely regarded as the most promising low-cost commercial solar cell solution to achieve over 30.0% efficiency. While laboratory perovskite/SHJ tandem solar cells have reached a record efficiency of 31.3%, the highest certified efficiency for industrial-scale perovskite/SHJ tandem solar cells remains at 25.2%. Addressing technical challenges such as interface leakage in all-textured SHJ bottom cells, current matching between the sub-cells, photoelectric losses in composite transparent conductive oxide (TCO) films, and the uniform coating of perovskite layers across larger areas has become crucial for enhancing the performance of these tandem solar cells.
To overcome these hurdles, the research team focused on developing a highly transparent ITO composite junction based on industrial-grade SHJ solar cells. By introducing a nickel oxide (NiOx)/2PACz ([2-(9H-carbazol-9-yl)ethyl]phosphonic acid) hybrid hole transport layer onto the ITO composite junction, they achieved optimal interface energy level alignment. Utilizing this as a foundation, they implemented a two-step co-evaporation plus spin-coating process to deposit high-quality perovskite layers conformally atop the SHJ solar cell. Their findings revealed that the NiOx intermediate layer facilitated the uniform self-assembly of 2PACz molecules on the full-textured surface, preventing direct contact between the ITO and the perovskite top cell. This eliminated the severe bulk leakage issues often encountered in conventional processes involving full-textured SHJ bottom cells. Thanks to this innovative interface engineering approach, the team achieved a third-party certified efficiency of 28.84% for industrial-scale perovskite/SHJ tandem solar cells (1.2 cm²).
This breakthrough represents another significant advancement in the development of industrial ultra-high-efficiency solar cell technology following the discovery of the anomalous Staebler-Wronski effect in SHJ solar cells incorporating amorphous silicon (a-Si:H) films (*Nature Energy*, 7 (2022) 427-437). The research received support from the "Honghu Special Project" strategic pilot science and technology initiative of the Chinese Academy of Sciences and the Key Laboratory of Microsystem Technology Fund Project.
**Figure 1:** Schematic illustration of the fabrication process for perovskite/SHJ tandem solar cells.
**Figure 2:** Structural design of the perovskite/SHJ tandem solar cell and its third-party certified efficiency.
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