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    Effect of GeI2 and GeBr2 incorporation on perovskite properties and performance of carbon-based perovskite solar cells
    (2023-04-01)
    Aunping, Namfon
    ;
    Kumlangwan, Pantiwa
    ;
    Towannang, Madsakorn
    ;
    Chanlek, Narong
    ;
    Kumnorkaew, Pisist
    CH<inf>3</inf>NH<inf>3</inf>PbI<inf>3</inf> (MAPbI<inf>3</inf>) film was prepared by a convective method, and its X-ray diffraction spectrum displays the tetragonal perovskite structure. GeI<inf>2</inf> and GeBr<inf>2</inf> powders dissolve poorly in a mixed dimethylformamide-dimethylsulfoxide (DMF-DMSO) solvent, but the introduction of 5 wt% 5-ammonium valeric acid iodide (5-AVAI) into the mixed DMF-DMSO solvent greatly promotes GeI<inf>2</inf> and GeBr<inf>2</inf> solubility. XRD spectra of the (5-AVAI)MAPbI<inf>3</inf>, MAGe<inf>x</inf>Pb<inf>1–x</inf>I<inf>3</inf>, and MAGe<inf>x</inf>Pb<inf>1–x</inf>Br<inf>2x</inf>I<inf>3–2x</inf> (x = 0.0625 and 0.125) films exhibit a tetragonal perovskite structure, but the film morphologies become rougher than that of the pristine MAPbI<inf>3</inf> film. Discontinuous islands are formed on MAGe<inf>x</inf>Pb<inf>1–x</inf>I<inf>3</inf> and MAGe<inf>x</inf>Pb<inf>1–x</inf>Br<inf>2x</inf>I<inf>3–2x</inf> (x = 0.125) films. X-ray photoemission spectroscopy (XPS) analysis detected the Ge element on all Ge-doped films. The best performance levels of the carbon-based hole transport layer-free MAGe<inf>x</inf>Pb<inf>1–x</inf>I<inf>3–x</inf> (x = 0.0625, η= 3.63%) and MAGe<inf>x</inf>Pb<inf>1–x</inf>Br<inf>2x</inf>I<inf>3–2x</inf> (x = 0.0625, η = 2.95%) perovskite solar cells are lower than that of the pristine MAPbI<inf>3</inf>–based perovskite solar cell (η = 5.28%). This is likely due to the increased surface roughness, pin-holes, isolated islands, and the decreased light absorbance of the Ge-doped films in comparison with the pristine MAPbI<inf>3</inf> film.
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    Influence of SCN− moiety on CH3NH3PbI3 perovskite film properties and the performance of carbon-based hole-transport-layer-free perovskite solar cells
    (2022-01-01)
    Prasan, Primprapha
    ;
    Aunping, Namfon
    ;
    Chanlek, Narong
    ;
    Kumlangwan, Pantiwa
    ;
    Towannang, Madsakorn
    CH<inf>3</inf>NH<inf>3</inf>PbI<inf>3</inf> perovskite films were prepared via a hot-casting method using six different CH<inf>3</inf>NH<inf>3</inf>I, PbI<inf>2</inf> and Pb(SCN)<inf>2</inf> solutions. Surface morphology of perovskite films with low SCN<sup>−</sup> dopant levels (0.0625 M and 0.125 M Pb(SCN)<inf>2</inf>) showed smooth surfaces and large grain sizes. However, with the high SCN<sup>−</sup> dopant levels (0.1875 M and 0.25 M Pb(SCN)<inf>2</inf>), rough surfaces were produced with pinholes. The crystal of pure CH<inf>3</inf>NH<inf>3</inf>PbI<inf>3</inf> (0 M Pb(SCN)<inf>2</inf>) film is a tetragonal perovskite structure. XRD spectra of all five Pb(SCN)<inf>2</inf> added films show the present of CH<inf>3</inf>NH<inf>3</inf>PbI<inf>3</inf> films and the additional peak at 12.66°. Rietveld refinement analysis reveals that the Pb(SCN)<inf>2</inf> addition causes the second phase PbI<inf>2</inf> formation along with the tetragonal MAPbI<inf>3</inf> perovskite film rather than the CH<inf>3</inf>NH<inf>3</inf>Pb(SCN)<inf>x</inf>I<inf>3-x</inf> perovskite formation. The carbon-based hole-transport-layer (HTL)-free perovskite (from 0.0625 M Pb(SCN)<inf>2</inf> dopant) solar cell is the optimal ratio in generating a promising cell efficiency, 6.34%, with a good efficiency retention of 79.43% after 30 days of testing in comparison to a pure CH<inf>3</inf>NH<inf>3</inf>PbI<inf>3</inf> (0 M Pb(SCN)<inf>2</inf> dopant) perovskite solar cell with an efficiency retention of only 26.92%. The great stability of the Pb(SCN)<inf>2</inf> added perovskite solar cells is attributed to the PbI<inf>2</inf> layer covered MAPbI<inf>3</inf> grains blocking oxygen and/or water molecules from degrading MAPbI<inf>3</inf> perovskite.