| Work Detail |
The triple junction solar cell is based on a superior perovskite solar cell with 15.0% efficiency modified with potassium thiocyanate (KSCN) and methylammonium iodide (MAI). According to its creators, the triple junction device presents a notable improvement in power conversion efficiency compared to more advanced devices.
Scientists led by King Abdullah University of Science and Technology (KAUST) in Saudi Arabia have manufactured a perovskite-perovskite-silicon triple junction solar cell with a new passivation strategy based on the use of potassium and thiocyanate.
“By combining modified broadband perovskite with synergistic additives and a meticulously designed device structure with optical and electrical considerations, we have successfully fabricated a 1 cm2 tandem perovskite/perovskite/silicon triple junction solar cell with an efficiency of power conversion of 26.4%,” the lead author of the research, Stefaan de Wolf, told pv magazine .
“This achievement not only represents the highest efficiency recorded in this field, but also validates the viability of the triple junction solar cell concept, laying a solid foundation for future research in this field,” added Fuzong Xu, co-author of the work.
Scientists tried to solve the problem of broad band perovskites using synergistic additives such as potassium thiocyanate (KSCN) and methylammonium iodide (MAI). In this way, the organic-inorganic perovskites are modified, while the passivation of defects, the enlargement of the grains, and the phase segregation induced by thiocyanate are mitigated.
For the top perovskite cells used in the triple junction device, the researchers used a perovskite material known as Cs0.1FA0.9PbBr2.1I0.9, which they modified with KSCN and MAI. For the intermediate cell they used the FAPbI3-based perovskite.
The triple junction cell was fabricated with a perovskite top cell with an efficiency of 15.0% and an energy bandgap of 1.98 eV, a perovskite middle cell with an efficiency of 22.9% and an energy bandgap of 1 .52 eV, and a lower silicon cell with an efficiency of 19.5% and an energy bandgap of 1.12 eV.
Tested under standard lighting conditions, the triple junction device achieved a power conversion efficiency of 26.4%, an open circuit voltage of 3.04 V, a short circuit current density of 11.9 mA/cm2, and a fill factor of 72.9%. The team claims that this remarkable performance is mainly due to the high efficiency of the perovskite bottom cell, which is one of the highest ever recorded for a cell with such a high bandgap.
“The choice of synergistic additives was strategic, mitigating the negative impact, accelerating the photoinduced phase segregation, of the confined thiocyanate ions by using their reaction with the MA+ to evaporate from the films in the form of MA and HSCN gas at 100 C ”Xu explained.
“Regarding the device structure, it is worth noting that the ultrathin gold interconnect layer, commonly used in perovskite/perovskite tandem solar cells, was found to be unsuitable for triple junction devices due to significant absorption in the region of response to the light of the central junction, thus limiting the overall efficiency,” added de Wolf.
The solar cell is described in the study “ Monolithic perovskite/perovskite/silicon triple-junction solar cells with cation double displacement enabled 2.0 eV perovskites ” with double cationic displacement), published in Joule .
“The 3-J perovskite/perovskite/Si solar cells with modified superior cells show a remarkable improvement in power conversion efficiency compared to the previous state-of-the-art ones, paving the way towards 3-J monolithic tandem solar cells based in perovskite with a higher efficiency than its 2-J counterparts,” the scientists conclude. |
