Inorganic and Pb-Free CsBi₃I₁₀ Thin Film for Photovoltaic Applications

Abstract

Computational, thin-film deposition, and characterization approaches have been used to investigate the all-inorganic lead-free CsBi3I10 as a candidate to act as a thin-film photovoltaic absorber. In this paper, CsBi3I10 was firstly predicted with a layer crystal structure of stable hexagonal phase-like Cs3Bi2I9 and then prepared by one-step coating also showing the high purity hexagonal phase and crystallinity, very consistent with the theoretical calculation. After solvent annealing, a high absorption coefficient of approximately 105 cm–1 in visible light and a suitable optical band gap of 1.78 eV were obtained for the CsBi3I10 thin film. The solar cell based on the CsBi3I10 perovskite thin film exhibited a high power conversion efficiency of 1.05%, good reproducibility, hysteresis-free behavior, and long-term stability. These results indicate that the performance of all-inorganic Pb-free perovskite solar cells can be further improved.

Inorganic and lead-free CsBi3I10 thin-film solar cell prepared by single-source thermal evaporation

“…4c, indicating that the CsBi 3 I 10 thin lms prepared by single source thermal evaporation have good absorption, and most of the absorption peaks begin at the wavelength of ~ 600 nm. Finally, according to absorption spectrum calculation, the band gap width of as-deposited lm and annealed lm was 1.79 eV and 1.78 eV respectively, which were close to the theoretical value of 1.77 eV reported in the literature [18].…”

“…Figure 5c shows a sharp absorption edge, indicating a high light absorption coe cient in the visible light range. The relationship between the band gap and optical absorption conforms to the Tauc relation, and the formula is αhν = C(hν − Eg) 1/2 , where α is the absorption coe cient, h is the Planck constan, C is the constant, and ν is the photon frequency [18]. The calculated energy band gap (E g ) of CsBi 3 I 10 lm is 1.83 eV, which is close to the previous band gap (E g ) of 1.79 eV calculated from the absorption spectrum.…”

“…Its stability can be improved by replacing MA + or FA + with Cs + . In the bismuth-based perovskite material CsBi 3 I 10 , Bi 3+ has the same potential as lead cation to obtain high e ciency 6S 2 6P 0 electron con guration to form the perovskite conduction band and valence band, and CsBi 3 I 10 band gap width of about 1.77eV is suitable as the perovskite solar cell absorption layer [18]. However, the highest photoelectric conversion e ciency of Cs 3 Bi 2 I 9 based perovskite solar cells prepared by traditional spinning coating method is only 3.2%.…”

“…At present, there are few studies on CsBi 3 I 10 thin lm solar cells, which are generally prepared by nonvacuum solution method. CsBi 3 I 10 thin lms are obtained by heat treatment after spinning the precursor solutions of CsI and BiI 3 [18]. However, the non-vacuum lm forming environment is di cult to ensure the repeatability of the process, and it is di cult to grow a continuous and uniform lm on a large area, resulting in low lm quality.…”

China’s progress of perovskite solar cells in 2019

“…Tin perovskites are not, however, the only option for lead-free materials. Shenzhen University developed a lead-free allinorganic perovskite material CsBi 3 I 10 as the photovoltaic absorber [80]. The perovskite showed a high absorption coefficient and an appropriate band gap of 1.78 eV based on which the formalstructure device achieved a PCE of 1.05% with no hysteresis.…”