Formamidinium Perovskite Solar Cells Fabricated Under Air Conditions: Additives and Pb-O bonds promote High Efficiency and Long-Term Stability
Sofia Masi a, K. M. Muhammed Salim a
a Institute of Advanced Materials (INAM), Universitat Jaume I, 12006 Castelló, Spain
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Oral, Sofia Masi, presentation 079
Publication date: 20th April 2022

The high-efficiency perovskite solar cells (PSCs) are mostly fabricated in a glovebox under controlled inert environments.[1] The formamidinium lead iodide (FAPI) perovskite is the most appealing Pb-based 3D halide perovskite for solar cell application because of its narrow bandgap.[1,2] However, the FAPI perovskite alpha-black phase is not stable at room temperature and is challenging to stabilize in an ambient environment due to its thermodynamic stability limitation.[2] We show that pure FAPI PSCs have significantly higher stability when prepared under ambient air compared to FAPI PSCs fabricated under nitrogen. The concomitant use of the N-methylpyrrolidone (NMP) and the preparation under air conditions is demonstrated as an effective combination to structurally stabilize the alpha-phase of the material and to improve the film quality, which is handled in the air for the fabrication of the solar cell. However, the most dramatic change observed among cells fabricated in a different environment is in the long term stability of unencapsulated devices where the T80 parameter, increases from 21 (in N2) to 112 days (in ambient) to 145 days if PbS quantum dots (QDs) are introduced as additives in air-prepared FAPI PSCs.[3] Furthermore, by adding methylammonium chloride (MACl) the PCE reaches 19.4% and devices maintain 100% of the original performance during two months of storage at ambient conditions. The increase of stability for air fabricated FAPI PSCs is correlated to the presence of Pb-O bonds only in the FAPI films prepared in ambient conditions,[4] thus opening the way to a new strategy for the stabilization in the air towards perovskite solar cells commercialization.

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