Hybrid lead halide perovskites are well-sought material because of both rich fundamental sciences and potential applications in the photovoltaic research community. However, two fundamental issues i.e., the stability in the external environment and the toxicity due to Pb are still remaining a concern. Here, we address the role of Sn-substitution and Pb-vacancy (Pb-■) in regulating the stability of CH3NH3Pb1-X-YSnX■YI3 perovskite using state-of-the-art hybrid density functional theory. The performance of the exchange-correlation functional (PBE, HSE06, HSE06+SOC) is carefully analyzed and validated w.r.t. available experimental results. We find that PBE and HSE06+SOC are giving exactly the opposite trend for thermodynamic stability. Therefore, the inclusion of SOC with hybrid functional is important in order to determine the stable phases using ab initio atomistic thermodynamics. We find pristine (CH3NH3PbI3) as the most stable configuration. However, Sn substitution X is also favorable for 0 ≤ X ≤ 0.5, whereas less stable for X &gt; 0.5. Our study further confirms that Pb vacancies (Pb-■) are not stable at all. This has been inferred from the lower formation energy of (charged) Sn substitution in the Pb8I24 framework as compared to a (charged) Pb-■ vacancy creation. For n-type and p-type host, the Sn substitution is more preferable than Pb-■ formation. Further, the optical properties and spectroscopic limited maximum efficiency (SLME) for thermodynamically stable configurations (Sn-substitutions) are also calculated and achieved the highest efficiency of 33% for MA8Pb7Sn1I24, whereas upto 50% Sn, the efficiency is reasonably good as compared to pristine. The stability of the doped perovskites is also confirmed at higher temperatures using ab initio Molecular Dynamics (ai MD) simulation. The lower formation energy, structure stability, direct p-p/s-p transition, high optical absorption coefficient (red shifted), stability at operational temperature and maximum solar cell efficiency of the CH3NH3Pb1−XSnXI3 (0 ≤ X ≤ 0.5) make it a promising candidate for the highly efficient solar absorber.

Role of defects in MAPbI3 to modulate optical absorption, and solar efficiency

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.