DFT study of electronic structure and mobility of pristine and fluorinated methylammonium lead halide perovskites (CH ₃ NH ₃ PbX ₃ , X = I, Br, Cl)

Abstract

Summary We present the electronic structure and mobility of pristine and fluorinated methylammonium lead halide perovskites (CH3NH3PbX3, X = I, Br, Cl) using DFT calculations. We find that both CH3NH3PbX3 and CF3NH3PbX3 exhibit direct bandgaps (1.5‐2.8 eV) which lies within the suitable bandgap regime for solar cell applications. The carrier mobilities of fluorinated MAPbX3 are much lower than pristine MAPbX3 indicating poor solar cell performance in spite of possible gain in stability due to enhanced hydrophobicity. The fluorination does not affect the chemical stability as is evident from the negative formation and cohesive energies, but an extremely high dipole moment (6.88 Debye) of CH3NH3+ may severely affect the charge carrier pathways.

Computational Screening of 2D All‐Inorganic Lead‐Free Halide Perovskites A3B2X9 for Photovoltaic and Photocatalytic Applications

“…[58][59][60] Hence, we developed an improved model to predict the PCE of 2D A 3 B 2 X 9 [53][54][55] and 3D halide perovskites (circles). [56,57] b) The hybridization of electronic states of 2D A 3 In 2 X 9 (left panel) and A 3 B 2 X 9 (B = Sb, Bi) (right panel) structures.…”

“…Carrier mobilities of 2D A 3 B 2 X 9 perovskites. a) Electron mobility (μ e ) of 2D A 3 B 2 X 9 structures (triangles), typical 2D semiconductors (squares),[53][54][55] and 3D halide perovskites (circles) [56,57]. b) The hybridization of electronic states of 2D A 3 In 2 X 9 (left panel) and A 3 B 2 X 9 (B = Sb, Bi) (right panel) structures.…”

Elucidating the photovoltaic effect of monoclinic K2SnBr6 by mixed-cation mixed-halide substitution from first-principles calculations

“…For most of the considered K (2−y) Rb y SnBr (6−x) I x compounds, the excitonic binding energy values are less than 130 meV along at least one of the considered crystallographic directions and hence are suitable for use in higher-efficiency solar cells. The charge carrier mobility in materials is yet another important parameter of semiconductors that needs to be considered while designing efficient absorbance layers for photovoltaic applications [58]. The charge carrier mobility determines how much faster the charge carriers can travel, and which further exert an effect on the electrical conductivity.…”

“…The shift in the band energy (∆E) with respect to a small lattice dilation (∆l) along a lattice (l 0 ) direction is interpreted as the DP [58,63], where ∆E i is the energy change in the i th band (CBM or VBM) under an appropriate compression or expansion (calculated at 0.5% step size) along three (x, y and z) directions. The notation l 0 is the equilibrium lattice constant (lattice parameter without any strain), and we have estimated the band structure of unit cells for five different deformed lattice constants: 0.990l 0 , 0.995l 0 , 1.000l 0 , 1.005l 0 and 1.010l 0 along three directions.…”

“…Therefore, when strain is applied, the bandgap shifts and straight lines are produced by varying the bottom of the CM and the top of the valence band for each perovskite material under consideration. The DP constant (E i values along three directions) can be calculated by taking the slope of the obtained straight lines [58,63]. Since we consider two directions in the present work, we have given (in table 3) the E i values along the x and y directions only.…”