Barium Acetate as An Additive for High-Performance Perovskite Solar Cells

Original Article:
Barium acetate as an additive for high performance perovskite solar cells

Yueming Wang, et al.

J. Mater. Chem. C, 2019,7, 11411-11418

10.1039/C9TC04067F

Defects within halide perovskite films limit the efficiency and stability of perovskite solar cells (PSCs). In the past, polymers, inorganic acids, fullerenes, organic halide salts, ionic liquids, etc. have been reported to be added to perovskites to enhance device performance. In addition, metal acetates, such as lead acetate, europium acetate, liquid zirconium acetate, etc., have also been reported to form high-quality perovskite films. In this work, the researchers introduced barium acetate (BaAc₂) as an additive into the MAPbI₃ perovskite precursor solution to fabricate high-performance PSC devices.

Mechanism of Barium Acetate in PSCs

The results of this study show that a very small amount of barium acetate can effectively improve the efficiency and stability of methylammonium lead trihalide perovskite solar cells, which may be attributed to the following aspects:

• Carbonyl-containing BaAc₂ can control the nucleation and growth of perovskite, leading to the formation of highly crystalline films with large grain sizes.
• The barium ions enter the crystal lattice of the perovskite, causing the lattice to expand. The generated PbI₂ and BaI₂ are located at grain boundaries (GBs), which can passivate defects and inhibit ion migration.
• Both the transition of the energy level to vacuum and the reduction of trap states in the barium acetate-doped perovskite film lead to a significant increase in V_oc.

General Procedure for The Synthesis of PSCs with Barium Acetate as An Additive

1. First prepare the perovskite precursor solution by dissolving MAI and PbI₂ in 1 mL of DMF: DMSO solvent.

2. The barium acetate powder was then added directly to the precursor solution.

3. The perovskite precursor solution was dropped on the plasma-treated ITO/P3CT-N substrate, and the perovskite layer was prepared by one-step spin-coating method.

4. The prepared film was annealed and cooled under different temperature conditions on a hot plate. Then the PC₆₁BM (6, 6-Phenyl C61 Butyric Methyl Ester) solution was spin-coated on the perovskite film to form an electron transport layer.

5. Finally, 20 nm C60, 8 nm BCP, and 100 nm Ag were deposited by thermal evaporation in a vacuum chamber using a metal shadow mask to obtain devices with the ITO/P3CTN/MAPbI₃/PC₆₁BM/C60/BCP/Ag structure.

Barium Acetate Significantly Improves the Performance of PSCs Devices

• The power conversion efficiency (PCE) of the original device was 18.99% with a V_oc of 1.09 V. The PCE of the BaAc₂-added device was 19.82%, and the V_oc was 1.13 V, which was significantly improved compared with the pristine device.
• The BaAc₂-added devices retained more than 90% of their initial PCE after thermal annealing at 90 °C for 400 h.

Chemicals Related in the Paper:

Catalog Number	Product Name	CAS Number
ACM543805	Barium Acetate	543-80-5
ACM5908645	Barium acetate monohydrate.	5908-64-5