Exploring the formation of formamidinium-based hybrid perovskites by antisolvent methods: in situ GIWAXS measurements during spin coating

Author(s)

Szostak, Rodrigo ^{[1, 2]} ; Marchezi, Paulo Ernesto ^[1] ; Marques, Adriano dos Santos ^[1] ; da Silva, Jeann Carlos ^[1] ; de Holanda, Matheus Serra ^[1] ; Soares, Marcio Medeiros ^[2] ; Nogueira Tolentino, Helio Cesar ^[2] ; Nogueira, Ana Flavia ^[1]

Affiliation

^[1] Univ Estadual Campinas, Chem Inst, Lab Nanotecnol & Energia Solar, UNICAMP, POB 6154, BR-13083970 Campinas, SP - Brazil

^[2] Brazilian Synchrotron Light Lab LNLS, Brazilian Ctr Res Energy & Mat CNPEM, BR-13083970 Campinas, SP - Brazil

• Document type: Journal article
• Source: SUSTAINABLE ENERGY & FUELS; v. 3, n. 9, p. 2287-2297, SEP 1 2019.
• Web of Science Citations: 1

Abstract

Antisolvent methods - solvent engineering and a Lewis base adduct approach - are the most used methods to prepare highly efficient perovskite solar cells (PSCs). These two methods differ only by the ratio between the perovskite (PVSK) and dimethyl sulfoxide (DMSO). In this study, the difference between these two methods and the effect of relative humidity (rH) on the crystallization process were evaluated by in situ Grazing-Incidence Wide Angle X-ray Scattering (in situ GIWAXS) using synchrotron radiation. The technique was applied to the first stages of formation of formamidinium-based perovskite films, under real preparation conditions of spin coating, and at different humidity conditions and time windows to inject the antisolvent. The higher amount of DMSO in the solvent engineering method prolongs the duration of the colloidal gel, which extends the time window for antisolvent injection and, as a consequence, facilitates obtaining films with a homogeneous morphology. Our results confirm that the formation of a cesium/formamidinium-based perovskite takes place through the conversion of 2H-4H hexagonal polytypes directly to a black perovskite without thermal annealing, independent of the rH or method employed. In contrast, a cesium-free, methylammonium/formamidinium-based perovskite follows the 2H-4H-6H polytype sequence. Interestingly, at higher amounts of DMSO and rH (40%), a pure iodide intermediate (MA(2)Pb(3)I(8)center dot 2DMSO) is formed in the cesium-free perovskite, which is undesirable in mixed halide perovskites. Our findings shed new light on the complexity of PVSK film formation, by identifying all crystalline phases in the process, and give clues to manage the composition and environment during film processing, and thus have an impact on efficiency optimization and solar cell manufacturing. (AU)

• FAPESP's process: 17/11986-5 - Generation and storage of New Energy: bringing technological development for the country
• Grantee: Ana Flávia Nogueira
• Support Opportunities: Research Grants - Research Centers in Engineering Program
• FAPESP's process: 17/12582-5 - Perovskites with mixed cations: Relationship between structure, composition, electronic properties and efficiency of solar cells
• Grantee: Rodrigo Szostak
• Support Opportunities: Scholarships in Brazil - Doctorate