The structural, electronic, and optical properties of organic–inorganic mixed halide perovskites CH ₃ NH ₃ Pb(I _{1− y} X _y ) ₃ (

Abstract

Methylammmonium lead iodide perovskites (CH 3 NH 3 PbI 3 ) have received wide attention due to their superior optoelectronic properties. We performed first-principles calculations to investigate the structural, electronic, and optical properties of mixed halide perovskites CH 3 NH 3 Pb(I 1−y X y ) 3 (X = Cl, Br; y = 0, 0.33, 0.67). Our results reveal the reduction of the lattice constants and dielectric constants and enhancement of band gaps with increasing doping concentration of Cl − /Br − at I − . Electronic structure calculations indicate that the valance band maximum (VBM) is mainly governed by the halide p orbitals and Pb 6s orbitals, Pb 6p orbitals contribute the conduction band minimum (CBM) and doping does not change the direct semiconductor material. The organic cation [CH 3 NH 3 ] + does not take part in the formation of the band and only one electron donates to the considered materials. The increasing trends of the band gap with Cl content from y = 0 (0.793 eV) to y = 0.33 (0.953 eV ) then to y = 0.67 (1.126 eV). The optical absorption of the considered structures in the visible spectrum range is decreased but after doping the stability of the material is improving.

Theoretical study of structural, electronic, and optical properties of mixed chalcogenide-halide bismuth perovskites CH3NH3BiChI2 (Ch = S, Se, Te)

“…Since our DFT calculations use the GGA, the calculated bandgap is underestimated compared with the experimental bandgap of 1.61 eV, 52) although our calculated bandgap of 0.83 eV is in good agreement with those calculated in the previous theoretical studies, 0.80 eV and 0.79 eV. 48,49) The calculated band gaps of MABiChI 2 are all vanishingly small: the gap < 0.01 eV for Ch = S, 0.06 eV for Ch = Se, and the closed gap for Ch = Te. The band gaps are all indirect.…”

“…32,50) The calculated structural parameters in this work are overestimated by about 3% compared with the experimental results, 31) while those parameters are in very good agreement with the results in the previous theoretical studies as shown in Table I. 48,49) On the other hand, the optimized structures of MABiChI 2 are contracted in the apical direction, that is, the lattice constant b is smaller by 1-2 Å than that of MAPbI 3 . Since the lattice constant b of MABiChI 2 is almost four times the Bi-Ch bond length, the contraction is more clearly understood when examining the ratios of M-I ap or M-Ch to the average of -M I eq 1 ( ) and -M I ; eq 2 ( ) the reduction ratios in the apical direction for MABiChI 2 are 16%, 12%, and 6% for Ch = S, Se, and Te, respectively.…”

Stability and optoelectronic property of low-dimensional organic tin bromide perovskites*

“…At the same time the low transport properties resulted from the spatial confinement of the carriers promote the effective radiative relaxation. [31][32][33][34][35][36][37] Furthermore, the excellent absorption within the whole visible light will lead to high quantum efficiency (QE).…”

Influence of Sr doping on the photoelectronic properties of CsPbX3 (X = Cl, Br, or I): a DFT investigation

“…Organic-inorganic hybrid halide perovskites ABX 3 (A = CH 3 NH 3+ or HC(NH 2 ) 2+ ; B = Pb 2+ ; X = Cl À , Br À , or I À ) have many potential applications in the photovoltaic and photoelectronic fields because of their excellent properties, such as a large absorption coefficient, high carrier mobility, and long carrier diffusion length. 1,2 However, their practical applications still face numerous challenges due to the toxicity of Pb 2+ and the poor long-term stability because of the easy decomposition of organic cations under hot or humid conditions. 3,4 Therefore, much effort has been devoted to resolve the stability and toxicity issues.…”