In the relentless pursuit of more efficient solar energy solutions, researchers have long been captivated by the potential of all-perovskite tandem solar cells. These innovative devices promise to surpass the limitations of traditional single-junction solar cells, but they’ve been held back by persistent issues with charge recombination losses. Now, a groundbreaking study published in InfoMat, the English translation of which is Information of Materials, offers a significant leap forward, addressing these challenges head-on.
At the heart of this research is a humble yet powerful lithium salt, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). When applied to narrow-bandgap (NBG) perovskites, this compound performs a remarkable feat: it simultaneously passivates both surface and bulk defects. This dual-action mechanism is a game-changer, as it tackles two major obstacles that have hindered the progress of all-perovskite tandem solar cells.
Yeonghun Yun, the lead author of the study from the School of Materials Science and Engineering at Kyungpook National University in Daegu, Republic of Korea, explains the innovative approach. “LiTFSI dissociates into Li+ and TFSI− ions,” Yun elaborates. “The TFSI− ions passivate halide vacancies on the perovskite surface, reducing nonradiative recombination, while the Li+ ions act as an interstitial n-type dopant, mitigating bulk defects and potentially suppressing halide migration.”
The implications of this discovery are profound. By extending the charge carrier lifetime and facilitating charge extraction, LiTFSI enables the creation of NBG devices with unprecedented power conversion efficiencies (PCE). The researchers achieved a PCE of 22.04% (certified at 21.42%) and an exceptional fill factor of 81.92%. When integrated into all-perovskite tandem solar cells, these advancements translate to PCEs of 27.47% and 26.27% for aperture areas of 0.0935 and 1.02 cm², respectively.
The commercial impact of this research could be transformative for the energy sector. As the demand for renewable energy sources continues to grow, the need for more efficient and cost-effective solar technologies becomes increasingly urgent. All-perovskite tandem solar cells, with their potential for high efficiency and low production costs, are poised to play a pivotal role in meeting this demand. The findings published in InfoMat, provide a crucial step forward in realizing this potential.
The underlying mechanism of LiTFSI passivation was further investigated through density functional theory calculations, adding a layer of scientific rigor to the study. This comprehensive approach not only validates the experimental results but also paves the way for future advancements in the field.
As the energy sector continues to evolve, the insights gained from this research could shape the development of next-generation solar technologies. By addressing the fundamental challenges associated with all-perovskite tandem solar cells, Yun and his team have opened new avenues for exploration and innovation. The journey towards more efficient and sustainable solar energy solutions is far from over, but with each breakthrough, we move one step closer to a brighter, more energy-secure future.