Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 12, Issue 30, Pages 34462-34469Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.0c10493
Keywords
orthorhombic CsSnI3; phase stability; oriented ligand; surface passivation; density functional theory
Funding
- Natural Science Foundation of Ningbo [2019A610056]
- National Natural Science Foundation of China [51974021]
- Fundamental Research Funds for the Central Universities
- 2018 Beijing Excellent Talents Training Support
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Lead-free orthorhombic CsSnI3 (B gamma-CsSnI3) perovskite has been emerging as one of the potential candidates of photovoltaic materials with superior performance. However, the instability induced by rapid reconstructive phase transition and the oxidation of Sn2+ greatly limits their future application. We thus reported a strategy, oriented pi-conjugated ligand passivation, for enhancing the stability of B gamma-CsSnI3, simulated using a B gamma-CsSnI3 slab model based on the first-principles computation. The phase stability was found to be strongly dependent on the orientations of phenylethylammonium (PEA(+)) ligands. The passivated B gamma-CsSnI3 slab with the ligand molecule axis along [414] was demonstrated as the most stable with the lowest adsorption energy (E-ads). Based on this configuration, the calculated formation energies (E-form) of half- and full-monolayer coverage were even more negative than that of yellow phase (Y-) CsSnI3 passivated by PEA(+) ligands, verifying the enhanced phase stability. Furthermore, the surface states could be effectively suppressed and the downshifted conduction band minimum (CBM) resulted in a reduced band gap for the completely capped B gamma-CsSnI3. Moreover, the CBM and the valence band maximum (VBM) of the system with complete coverage were respectively donated by the surface and bulky components of the slab, which might benefit the separation and transfer of photogenerated carriers.
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