Organic–inorganic hybrid halide perovskites are promising optoelectronic materials with a wide range of applications including solar cells. The toxicity of lead perovskite, however, hampers the commercialization. While tin (Sn) perovskite is a promising alternative, the facile oxidation of Sn(II) to Sn(IV) causes a high density of defects, resulting in lower solar cell efficiencies.
We previously developed high purity, solvent-coordinated tin halide complexes such as SnI₂(dmf) for use as tin perovskite precursor materials.¹ Although this, combined with our original film fabrication method,² resulted in improved device performance, the perovskite layers still contain Sn(IV) impurities which most likely formed after the starting materials were purified.
Here, we show that Sn(0) nanoparticles in the perovskite precursor solution can scavenge Sn(IV) impurities, and demonstrate that this treatment leads to Sn(IV)-free perovskite films.³ These nanoparticles are generated by the selective reaction of 1,4-bis(trimethylsilyl)-2,3,5,6-tetramethyl-1,4-dihydropyrazine (TM-DHP) with SnF₂. Using this nanoparticle treatment, the power conversion efficiency of Sn-based solar cells reaches 11.5%, with an open-circuit voltage of 0.76 V. Our nanoparticle treatment is a simple and broadly effective method that improves the purity and electrical performance of tin perovskite films.

1) M. Ozaki, Y. Shimakawa, Y. Kanemitsu, A. Saeki, A. Wakamiya, et al., ACS Omega 2017, 2, 7016. 2) J. Liu, M. Ozaki, Y. Kanemitsu, A. Saeki, R. Murdey, A. Wakamiya, et al., Angew. Chem., Int. Ed. 2018, 57, 13221. 3) T. Nakamura, T. Sasamori, H. Ohkita, Y. Kanemitsu, A. Wakamiya, et al., Nat. Commun. 2020, 11, 3308.

Richard Murdey

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