The development of photovoltaics (PVs) has recently shown all-inorganic perovskites to be very promising because they may be able to achieve greater thermal stabilities than hybrid perovskite solar cells made of both organic and inorganic materials. Despite any potential benefits, the majority of solar cells made entirely of inorganic perovskites have low energy conversion rates and short carrier lifetimes.
Non-radiative recombination, a process through which charge carriers recombine and release phonons rather than photons, is largely to blame for the energy loss that results in these underwhelming performances. All-inorganic perovskite solar cells have so far been difficult to use in practice because of the energy losses and decreased efficiencies brought on by this process.
The efficiency and carrier lifetimes of all-inorganic perovskite solar cells may be enhanced thanks to a recent strategy developed by scientists at the Chinese Academy of Sciences. This approach, described in Nature Energy, is based on a technique called surface in situ reconstruction (SISR), which involves subjecting materials to particular chemicals in order to create new layers on their surface.
“Using CsF treatment, we devised a SISR method for inorganic perovskite that can decrease non-radiative recombination while also promoting hole extraction.”Xinbo Chu, Qiufeng Ye and their colleagues wrote in their paper.
“We developed a SISR strategy for inorganic perovskite by CsF treatment, which can suppress non-radiative recombination and promote hole extraction simultaneously,” wrote Xinbo Chu, Qiufeng Ye, and their colleagues in their paper. When fluorine was added, carrier lifetime increased from 11.5 ns to 737.2 ns, effectively passivating surface flaws. Additionally, a graded heterojunction that has a wider bandgap can be produced to make hole extraction easier.
The researchers’ SISR method entails treating an inorganic perovskite with cesium fluoride (CsF), a substance that can inhibit non-radiative recombination while also facilitating hole extraction. They applied this technique specifically to CsPbIxBr3x, an inorganic perovskite that is frequently used to make absorbers for PVs.
The performance of an all-inorganic perovskite solar cell based on CsPbIxBr3x that was treated using Chu, Ye, and their colleagues’ method was then evaluated through a series of tests. The researchers’ results were very encouraging, indicating that their suggested strategy had successfully increased the solar cell’s efficiency and increased its carrier lifetimes.
Chu, Ye, and their coworkers stated in their paper that “the SISR reaction mechanism was verified from both kinetic calculations and experiments.”. A CsPbIxBr3x solar cell with SISR managed to achieve a 21 point 02 percent efficiency with a high open-circuit voltage of 1 point 27 volts and a fill factor of 85 point 3 percent.”.
The most recent research by this group of scientists may have important ramifications for the creation of stable, effective, and dependable all-inorganic perovskite PVs. It could soon inform fresh research examining the potential of other SISR techniques for limiting non-radiative recombination losses in inorganic perovskites, in addition to informing the development of new solar cells.
Although Chu, Ye, and their colleagues have only tested their method on CsPbIxBr3x thus far, they think it could be used with other inorganic perovskites. In order to confirm its generalizability, it could subsequently be tested on samples of different materials and solar cells.
More information: Xinbo Chu et al, Surface in situ reconstruction of inorganic perovskite films enabling long carrier lifetimes and solar cells with 21% efficiency, Nature Energy (2023). DOI: 10.1038/s41560-023-01220-z