Narrow Band gap Bismuth Tri-iodide via Cesium Tin Iodide Doping for Lead-free Solar Cells Application
Aditya Wahyu Anugrah a, Itaru Raifuku a b, Hidenori Kawanishi a, Yukiharu Uraoka a
a Nara Institute of Science and Technology, 日本 〒630-0192, 生駒市, Japan
b Aoyama Gakuin University
Poster, Aditya Wahyu Anugrah, 068
Publication date: 24th October 2023

Bismuth (Bi)-based materials have been studied as the potential candidates to replace the toxic lead (Pb)-containing compounds in perovskite solar cells due to their non-toxic nature and use in biomedicine [1]. The effective ionic radius of Bi is similar to that of Pb and Bi perovskites have been shown to be stable in both dry and humid air [2,3]. However, the wide band gap of Bi-based perovskites limits their further application in solar cells. This study aims to address this issue by developing a general doping strategy to achieve narrow band gap bismuth tri-iodide (BiI3).

We here report that BiI3 material doped with CsSnI3 shows significantly reduced bandgap compared to that of undoped one (1.75 eV). It was as small as 1.41 eV when we mixed the precursor solution at a volume ratio of 1.6 (CsSnI3:BiI3) which was confirmed by Tauc plots. X-ray photoelectron spectroscopy (XPS) analysis revealed that the Fermi level (EF) shifted considerably toward the conduction band minimum (CBM) due to CsSnI3-doping. The estimated energy band diagram is schematically illustrated in the paper. Our study demonstrated that CsSnI3-doping can modify the band gap, CBM, and VBM of BiI3. The power conversion efficiency of the device was found to be improved up to 0.106%.

The authors would like to thank to NAIST University Fellowship for funding this research

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