Scientists at Germany’s Fraunhofer Institute for Solar Energy Systems (ISE) have developed a groundbreaking triple-junction solar cell using a perovskite-perovskite-silicon subcell configuration. This innovative design has achieved an impressive efficiency of 20.1% and an open-circuit voltage exceeding 2.8 V.
Triple-junction solar cells are a type of multijunction solar cell that utilize three distinct subcells to capture light across different wavelength ranges. The key advantage of this design is its ability to achieve higher overall efficiencies compared to single-junction solar cells.
The research team at Fraunhofer ISE incorporated perovskite materials with energy bandgaps ranging from 1.56 V to 1.83 V in the perovskite absorber. This combination of bandgaps is not yet optimized for a triple-junction solar cell, but the focus of the study was on process optimization and subcell integration. The findings are expected to be applicable to other perovskite compositions.
The triple-junction solar cell consisted of three subcells with different architectures. The bottom cell included indium tin oxide (ITO) substrate, a hole transport layer (HTL) made of poly-triarylamine (PTAA), and a gold (Au) metal contact. The second subcell used a silver (Ag) metal contact and an anti-reflective coating based on magnesium fluoride (MgF2). The upper subcell featured a carbazole (2PACz) layer and an anti-reflective coating based on magnesium fluoride (MgF2).
Under standard illumination conditions, the triple-junction solar cell achieved a power conversion efficiency (PCE) of 20.0%, an open-circuit voltage of over 2.8 V, a short-circuit current density of 8.9 mA/cm², and a fill factor of approximately 78%. The high voltage attained indicates the suitability of the solar cell’s fundamental characteristics for improved efficiency.
While this triple-junction solar cell design demonstrates promising results, further optimizations are necessary to surpass the performance of perovskite/silicon dual-junction solar cells. Additionally, the long-term stability of these solar cells under standard test conditions and elevated temperatures needs to be addressed in future research.
The research conducted by Fraunhofer ISE highlights the immense potential of perovskite and silicon in advancing photovoltaics. As the team continues scaling up the development of perovskite-silicon tandem solar cells, they believe triple-junction solar cells hold great promise for future advancements in the field.
– Fraunhofer Institute for Solar Energy Systems ISE