A perovskite solar cell was “sprinkled with salt” and achieved an efficiency of over 25%

Eu(TFSI) salt enabled perovskite cells to instantly gain high conductivity and ensure perfect operation without the need for further processing.

Researchers from Northwest Polytechnic University of China have proposed a new lithium-free doping strategy for perovskite solar cells. Salt-doped photovoltaic device achieves record efficiency of 25.45%, pv-magazine.com reports , made from spiro-OMeTAD, which is reported to provide excellent levels of efficacy and stability.

Spiro-OMeTAD is usually doped with a compound known as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to improve holes and conductivity. However, this type of doping requires long-term air oxidation for 24 hours, which is an obstacle for the commercial production of perovskite photovoltaic cells.

200% Deposit Bonus up to €3,000 180% First Deposit Bonus up to $20,000

Insufficient doping efficiency of this post-processing process can lead to the retention of unreacted reagents and/or harmful by-products in the doped spiro-OMeTAD layer, adversely affecting device performance. In addition, a significant problem limiting their practical application is the trade-off between high efficiency and stability.

To solve this problem, scientists used a salt known as Eu(TFSI) for doping. This salt can generate oxygen and promote the pre-oxidation of spiro-OMeTAd. Unlike conventional doping, air-exposed LiTFSI enables perovskite cells to instantly achieve high conductivity and achieve ideal performance without the need for further processing.

Using this doping strategy, the researchers built a solar cell with a fluorine-doped glass substrate tin oxide, an electron transfer layer based on titanium oxide, a perovskite absorber and a gold contact.

Tested under standard lighting conditions, this solar cell achieved an energy conversion efficiency of 25.45%, an open-circuit voltage of 1.210 V, a current density short circuit of 25.41 mA cm2 and fill factor of 82.50%. A LiTFSI-doped control cell with the same architecture achieved an efficiency of only 23.19%.