Scientists at the University of Queensland in Australia have fabricated a solar cell based on a mixture of 2D and 3D salts. They claim that the cell is more moisture-resistant and durable than “conventional” perovskite cells based on 3D materials alone.
The cell should include the advantages of cells based on two-dimensional (2D) perovskites, which generally provide more hydrophobicity and thermal stability than “conventional” 3D structures. But it should also include the benefits of 3D perovskite cells, which can offer strong light absorption, good charge carrier transport, and higher power conversion efficiencies.
In “Engineering fluorinated-cation containing inverted perovskite solar cells with an efficiency of >21% and improved stability towards humidity,” which was recently published in Nature Communications, the cell was built with an inverted configuration (p–i–n). The scientists describe it as a solution with potential low-temperature preparation processes, reduced hysteresis, and improved long-term stability under ultraviolet (UV) light, compared to standard n-i-p architectures.
The device incorporates a fluorinated lead salt – the 2-(2,3,4,5,6-pentafluorophenyl)ethylammonium iodide (FEAI) – into the processing solution, which is normally used to form the 3D methylammonium lead iodide (MAPbI3).
“We demonstrate that small quantities of the additive enhance the performance relative to the neat MAPbI3 in terms of power conversion efficiency and stability to humidity and temperature,” the Australian team explained. “We also show that when the FEAI concentration in the processing solution is above a critical level the performance of the cells decreases.”
They said the simple addition of 0.3 mole percent of a fluorinated lead salt into the three-dimensional methylammonium lead iodide perovskite, via a low-temperature fabrication process, allows the cell to achieve a power conversion efficiency of 21.1%, without the use of an anti-reflective coating. The cell also exhibited an open-circuit voltage of 1.12 V, a short-circuit current of 22.4 mA/cm2, and a fill factor of 84%. They also claimed that there is no evidence for the formation of a 2D-perovskite layer, nor well defined large 2D crystals.
“We believe this efficiency is competitive with the highest reported for inverted perovskite solar cells composed of a mixture of 2D and 3D salts in the precursor solution, although with a less complex active layer,” the group said.
Additives that can form 2D Ruddlesden–Popper (RP) perovskite films when mixed with a 3D perovskite do not necessarily have to be used at a concentration to form a 2D/3D mixed perovskite film that will stabilize the cells and ensure performance, they added. Ruddlesden-Popper (RP) perovskites have attracted extensive attention in photovoltaics in recent years because they are highly stable, without sacrificing too much efficiency.
“The results show that if there is no FEAI in the active layer composition (pure MAPbI3) or there is too much additive (as little as a few percent), then the devices have poorer performance,” the scientists concluded. “The addition of 0.3 mol% of FEAI led to perovskite films in which there was no observable 2D phase and devices with the best performance.”
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When I read about these harx-to-achieve “miniscule” improvements in Solar Cell Efficiencies one feels like applauding….
However…. many “exotic materials and technologies” are proposed with some very very dangerous sounding names… lead.. arsenic… this and that ..dium and toxic material sounding substances too.
If Solar Panels that promise to put an end to Pollution leave behind a legacy of toxic substances like nuclear, fossil plants/fuels, Electric Batteries, etc…. has one not defeated the main purpose behind the wide use of Solar Panels…. to eliminate Pollution and NOT leave behind a legacy of toxic waste behind??
So… one must be also made aware and demand proper Accounting and Disposal of Polluting materials used in the manufacture as well as “after-life”…. just Efficiency Imorovements are inadequate!!
The trick is to have companies interested in the old panels, as active area only to complex remake opportunities. Even the AR coats can be brought to structural light ingress and various self cleaning schemes, leaving the gram amounts of Pb, As, Co, In, Ga to be progressively (formulated and crystallized,) esconsed in new active core layers. Then plenty of industrial remediation turning undersides to environmental active layers and decent new brackets and busses, junctions and on toward soil interfaces.
Not a lot of added accounting unless you’re making food while pulling apart a wrecked array, which I guess is still how wars are broken up.
On the other hand I hear forever from IoT nubbins how they sense at kHz how much air they move ostensibly keeping air fresh when they know nothing of what green or roadborne hell they are advancing or dessicating. Those macromolecular sensors could develop a little faster into their placeholders.
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