Genevieve Hall1 William Petuskey1 Michael Stuckelberger1 Mariana Bertoni1

1, Arizona State University, Tempe, Arizona, United States

Commercial deployment of perovskite solar cells (PSCs) requires extending their service lifetimes from months to years.1 Grain boundaries exacerbate perovskite material degradation through several different mechanisms. The degradation rate of PSCs due to water exposure is linearly dependent on perovskite crystal size.2 Similarly, grain size and uniformity are correlated to extent of degradation by light and oxygen.3 Additionally, smaller grain sizes and reduced crystallinity increase ion migration.4

To mitigate these issues, the research community is attempting to grow thin (~200 nm), wafer-scale (~10 cm x 10 cm), perovskite crystals. Chen et al. recently grew small monocrystalline perovskite films (on the scale of mm x mm x nm) by drawing precursor solution up between two substrates via capillary action and heating to crystallize.5 This unusual precursor deposition method allows the absorber layer to be the last step in device fabrication, which increases the number of possible materials for charge transport layers, contacts, and substrates. Lee et al. recently fabricated monocrystalline perovskite films (cm x ┬Ám x nm) by intensely heating concentrated precursor solution at the deposition point, which resulted in instant crystallization.6

We demonstrate the growth of large (cm x cm x nm) monocrystalline perovskite films by combining the capillary precursor deposition method with intense local heating. We will report the effects of precursor concentration, temperature, substrate roughness, and substrate separation distance on morphology and crystallinity. Film surface area and crystallinity are assessed via confocal optical microscopy and x-ray diffraction, respectively, while film thickness is determined by atomic force microscopy. Film homogeneity is further characterized via submicron-scale photoluminescence and Raman mapping. These studies will improve understanding and control of perovskite film growth, and help enable commercial deployment of PSCs.

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3. Sun, Q.; Fassl, P.; Becker-Koch, D.; Bausch, A.; Rivkin, B.; Bai, S.; Hopkinson, P.E.; Snaith, H.J.; Vanyzof, Y. Adv. Energy Mater. 2017, 7, No. 1700977.
4. Hu, M.; Bi, C.; Yuan, Y.; Bai, Y.; Huang, J. Adv. Sci. 2016, 3, No. 1500301.
5. Chen, Y.-X.; Ge, Q.-Q.; Shi, Y.; Liu, J.; Xue, D.-J.; Ma, J.-Y.; Ding, J.; Yan, H.-J.; Hu, J.-S.; Wan, L.-J. J. Am. Chem. Soc. 2016, 138, 16196-16199.
6. Lee, L.; Baek, J.; Park, K.S.; Lee, Y.-E.; Shrestha, N.K.; Sung, M.M. Nat. Commun. 2017, 8, No. 15882.