Since the efficiency of silicon solar cells—the dominant technology in photovoltaics—is nearing its practical efficiency limit, silicon-based tandems are natural successors. The challenge is to identify a top-cell partner that is efficient, cost effective, and has fabrication processes that are compatible with silicon cells. Among all the top-cell materials that are presently under investigating, perovskites stand out due to their solution-processability, bandgap tunability, and unprecedented efficiency increase.
Perovskite/silicon tandem has the potential to achieve >30% efficiency. But because solution processing for perovskite deposition requires a smooth silicon surface, the high surface reflectance and diminished light scattering into the silicon bottom cell limit photo-generated current and device efficiency. Although costly high-vacuum processes may be able to accommodate textured silicon surfaces for improved efficiency, manufacturing would not be cost-competitive with single-junction silicon technology.
Researchers at Arizona State University have developed a new perovskite/silicon tandem architecture that allows the perovskite cell to be solution-processed onto textured silicon cells. An optimal texture size has been identified that is small enough to enable cost-effective solution processing while increasing light scattering for improved device efficiency. Surface texture can be introduced using a variety of methods including wet chemical etching, plasma dry etching, and nanoimprint lithography.
• Perovskite/silicon tandem photovoltaic devices
Benefits and Advantages
• Requires minimal modification to silicon device processing
• Improves device efficiency through increased light scattering
• Retains suitability for low-cost solution processing