A theoretical investigation of structural, mechanical, electronic and thermoelectric properties of orthorhombic CH3NH3PbI3

Electronic and optical properties of orthorhombic (CH3NH3)BX3 (B = Sn, Pb; X = F, Cl, Br, I) perovskites: a first-principles investigation

“…Table 4 summarizes our calculated band gaps of orthorhombic (MA)BX 3 (B ¼ Sn, Pb; X ¼ F, Cl, Br, I) perovskites, which are in good agreement with available theoretical results of (MA)PbI 3 and (MA)SnX 3 (X ¼ Cl, Br, and I). 1,17,32,33 Comparing with the GGA + PBE calculations without including SOC (2.685 eV for (MA)PbCl 3 ) shown in Fig. S9 of the ESI, † a much lower band gap (1.614 eV) was obtained (but still stay as direct band-gap semiconductors) which is consistent with the band-gap decrease predicted by Lang et al 5 In addition, the contribution of the p-orbitals is much lower when SOC is included.…”

“…33 For (MA)PbI 3 , our geometry simulation results (Tables 1 and 2) agree well with that of using PBE. 17,39 However, the PBEsol appears to better approximate the b and c lattice constants as compared to the experimental results, though it is outperformed by PBE for the a lattice constant. 17 For the available Sn-containing perovskite sources, the Grimme van der Waals correction was used to account for the dispersion interactions, resulting in lower lattice constants than ours.…”

“…17,39 However, the PBEsol appears to better approximate the b and c lattice constants as compared to the experimental results, though it is outperformed by PBE for the a lattice constant. 17 For the available Sn-containing perovskite sources, the Grimme van der Waals correction was used to account for the dispersion interactions, resulting in lower lattice constants than ours. 32,33 This lack of dispersion interaction correction and the precision of exchange-correlation functional (PBE over HSE06) likely explain the systematic over-estimation of lattice constants in our results.…”

“…In contrast to the rich available data for the cubic phase of this halide perovskite family which has been published in the literatures, 5,12,15,16,[18][19][20][21][22][23][24][25][26][27][28][29][30][31] only a few computational studies focus on the orthorhombic phase of (MA)PbI 3 and (MA)SnX 3 (X ¼ Cl, Br, and I). 1,17,32,33 As an example, Table 2 lists our optimized atomic fractional coordinates of MAPbI 3 in comparison with the reported structures in Materials Project, 39 while the optimized atomic coordinates of the rest of the seven structures of (MA)BX 3 are provided in Tables S1-S7 of the ESI. † Overall, as one can see from Tables 1, 2 and S1-S7, † our optimized structures of (MA)BX 3 are in good agreement with available experimental data and other theoretical modeling results.…”

“…12 In the literature, the electronic and optical properties of the high-temperature cubic phase (MA)BX 3 (B ¼ Sn, Pb; X ¼ Cl, Br, I) were widely studied both by computational calculations and experimental measurements. 5,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] However, few studies look into these perovskites in their low-temperature phases, particularly the orthorhombic phase. One possible reason lies in the fact that many of these structures may only be stable at very low temperatures.…”