Dimethylammonium Addition to Halide Perovskite Precursor Increases Vertical and Lateral Heterogeneity

Journal Article · 12 December 2021 · ACS Energy Letters

DOI: https://doi.org/10.1021/acsenergylett.1c02302 · OSTI ID:1841362

Jariwala, Sarthak  ^[1]; Kumar, Rishi E. ^[2]; Eperon, Giles E.  ^[3]; Shi, Yangwei ^[1]; Fenning, David P.  ^[2]; Ginger, David S.  ^[1]

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1. Univ. of Washington, Seattle, WA (United States)
2. Univ. of California, San Diego, CA (United States)
3. National Renewable Energy Lab. (NREL), Golden, CO (United States); Swift Solar Inc., San Carlos, CA (United States)

Adding a large A-site cation, such as dimethylammonium (DMA), to the perovskite growth solution has been shown to improve the performance and long-term operational stability of halide perovskite solar cells. To better understand the origins of these improvements, we explore the changes in film structure, composition, and optical properties of a formamidinium (FA), Cs, Pb, and mixed halide perovskite following the addition of DMA to the perovskite growth solution in the ratio of DMA_0.1FA_0.6Cs_0.3Pb(I_0.8Br_0.2)₃. Using time-of-flight secondary-ion mass spectrometry (TOF-SIMS), we show that DMA is indeed incorporated into the perovskite, with a higher DMA concentration at the surface. Using a combination of photoluminescence (PL) microscopy and photoinduced force microscopy-based (PiFM) nanoinfrared (nanoIR), we demonstrate that incorporating DMA into the film leads to increased local heterogeneity in the local bandgap and clustering of the local formamidinium (CH₅N₂⁺) composition. In addition, using nano-X-ray diffraction, we demonstrate that DMA incorporation also alters the local structural composition by changing the local d-spacing distribution and grain size. Our results suggest that compositional variations in the organic cations at the A-site drive the structural heterogeneity observed in the case of DMA-incorporated films. Our results also suggest that while current DMA-additive-based approaches do have benefits to operational stability and device performance, process optimization to achieve local compositional and structural homogeneity could further boost both of these gains in performance, bringing further gains to solar cells using DMA additives.

• Research Organization: Georgia Inst. of Technology, Atlanta, GA (United States); National Renewable Energy Laboratory (NREL), Golden, CO (United States); Univ. of Colorado, Boulder, CO (United States); Univ. of Washington, Seattle, WA (United States)
• Sponsoring Organization: National Science Foundation (NSF); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office; USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office; USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC36-08GO28308; EE0008747
• OSTI ID: 1841362
• Report Number(s): NREL/JA-5900-81917; MainId:82690; UUID:1e14934b-b953-40ad-ae79-79b62500e464; MainAdminID:63676
• Journal Information: ACS Energy Letters, Journal Name: ACS Energy Letters Journal Issue: 1 Vol. 7; ISSN 2380-8195
• Publisher: American Chemical Society (ACS)Copyright Statement
• Country of Publication: United States
• Language: English