Slot-die coating large-area formamidinium-cesium perovskite film for efficient and stable parallel solar module

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Science Advances  30 Apr 2021:
Vol. 7, no. 18, eabg3749
DOI: 10.1126/sciadv.abg3749
  • Fig. 1 Precursor ink engineering to stabilize the wet film.

    (A) Semi–in situ observation of perovskite precursor film morphology evolutions over time with an optical microscope (scale bar, 100 μm). The perovskite precursors dissolved in DMF, DMF-NMP, and DMF-NMP-DPSO are denoted as precursors 1, 2, and 3, respectively. (B) Optical absorbance evolution of perovskite precursor films as a function of time at the wavelength of 550 nm. a.u., arbitrary units. (C) TGA of perovskite inks without the addition of CsBr. (D to F) Semi–in situ XRD measurements of precursor films based on DMF (D), DMF-NMP (E), and DMF-NMP-DPSO (F). (G) DLS spectra of FACs perovskite precursor solutions. The concentrations of all samples are 0.5 mM. Unless otherwise specified, DMF, DMF-NMP, and DMF-NMP-DPSO represent the perovskite precursors dissolved in different solvents with or without additive, and the precursor films were dried in ambient air at room temperature during the measurements.

  • Fig. 2 Interaction between the solvent or additive molecules and perovskite precursor species.

    (A to C) FTIR spectra of fingerprint regions for C═O and S═O stretching vibrations. (A) C═O stretching detected from DMF (solution, black), PbI2·DMF (powder, red), FAI (powder, blue), and FAI·PbI2·DMF (powder, orange). (B) C═O stretching detected from NMP (solution, black), PbI2·NMP (powder, red), and FAI·PbI2·NMP (powder, orange). (C) S═O stretching measured for DPSO (powder, black), PbI2·DPSO (powder, red), and FAI·PbI2·DPSO (powder, orange). The blue line represents the spectra of FAI (powder). (D to I) Molecular structures resulting from DFT calculations. Molecular structures of (D) PbI2·DMF, (E) PbI2·NMP, (F) PbI2·DPSO, (G) FA+·DMF, (H) FA+·NMP, and (I) FA+·DPSO. (J) Interaction energy of solvent or additive molecules with the perovskite precursor species FA+ and PbI2.

  • Fig. 3 Crystal structure of intermediate films and surface morphology evolutions of the perovskite films.

    (A to C) XRD characterization of three precursor wet films immersed into antisolvent at different time stages for 2 min without annealing treatment. (A) DMF, (B) DMF-NMP, and (C) DMF-NMP-DPSO. (D) Scanning electron microscopy (SEM) images of precursor films (DMF, DMF-NMP, and DMF-NMP-DPSO are denoted as precursors 1, 2, and 3, respectively) immersed into antisolvent at different wet film holding time stages for 2-min AST and annealed at 150°C for 30 min. “W/o AST” represents the films that are directly heated (150°C for 30 min) after coating. Scale bar, 1 μm.

  • Fig. 4 Optical and electronic properties of large-area perovskite films.

    (A) Optical image of large-area perovskite films. (B) Uniformity of large-area perovskite film on glass substrate characterized by PL mapping. (C) Schematic illustration of the fabricated large-area perovskite film cut into 12 pieces of 4 cm by 4 cm films. (D) Absorption spectra of 12-piece cut from a large-area perovskite sample. (E) Average TRPL lifetime distribution of 12-piece cut from a large perovskite film sample. (F) J-V curves of 12 PSCs with an active area of 1 cm2; the corresponding perovskite films were cut from a large-area perovskite film. Photo credit: Zhichun Yang, Huazhong University of Science and Technology.

  • Fig. 5 PSM structure and performance.

    (A) High-resolution cross-sectional SEM image of a complete PSM. (B) Three-dimensional structure schematic diagram of the designed module connected in parallel. (C) Cross-sectional schematic illustration of the fabricated module coupled with the deposition methods of the functional layers. (D) I-V curves of PSMs including a stabilized efficiency output and the device performance before and after stabilized test. FF, fill factor. (E) Reproducibility of PSMs (30 samples were tested); the inset is the optical image of some fabricated modules. Photo credit: Zhichun Yang, Huazhong University of Science and Technology.

  • Fig. 6 PSM stability.

    (A) Operational stability of PSMs encapsulated by a cover glass or ALD Al2O3/cover glass under continuous light irradiation (the light source for the aging test was generated by a 1-sun equivalent white-light LED array) with MPP tracking at the temperature around 50°C in ambient air. (B) Stability of the ALD Al2O3/cover glass–encapsulated module under real day/night cycling without any humidity control. The PCE evolutions are obtained from the average values of the forward and reverse scans.

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