Fig. 1. Illustration of shear coating process. The illustration shows the formation of MHP film when shear coating method is applied. The upper plate is a glass blade and the lower plate fixed on a hot plate is an ITO glass substrate. MHP precursor solution is located on the area between these glasses. The film is fabricated by moving precursor solution with the upper plate in one direction.
Fig. 2. The optical microscopy image (a), the grain size distribution (b) of MHP film deposited by the shear coating and the scanning electron microscopy image(c) and the grain size distribution (d) of MHP film deposited by the spin coating.
Fig. 3. The optical microscopy images and grain size distributions of MHP films when DMF (a and b) and mixture of GBL and DMSO (7:3 volume ratio) (c and d) are used as solvents of MHP precursor solutions. (scale bar: 100 μm)
Fig. 4. Effects of substrate temperatures on the grain growth of the shear coating process. Average size of MHP grains increases as substrate temperature increases from 100oC to 160oC when GBL:DMSO=7:3 solution is used as solvent of MHP precursor solution. However, there is no tendency of grain size according to the substrate temperature when DMF is used. (scale bar: 100 μm)
Fig. 5. Effects of shear rate and concentration of MHP precursor solutions on the grain growth. Grain morphology changes as shear rate increases from 2 mm/s to 6 mm/s. (scale bar: 100 μm)
Fig. 6. Effects of shear rates on the surface morphology of MHP films. The MHP films are deposited with 35wt% precursor solution, and different shear rates of 4~6 mm/s are applied on these films.
Fig. 7. XRD result of MHP film deposited by shear coating (*ITO). XRD data shows existence of two substances, CH3NH3PbI3 and ITO. The indices and star symbols demonstrate CH3NH3PbI3 and ITO, respectively.
Fig. 8. Effects of the annealing time and temperature on J-V performances(a and b) of MHP solar cells of which light absorption layers are made by shear coating. (c) The influence of the annealing temperature on the PL of the shear coated MHP layers.
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