Fig. 5: Band gap engineering.
From: Automated design of hybrid halide perovskite monolayers for band gap engineering
a, b The Pearson correlation coefficients between band gaps and structural parameters for Pb-I and Cd-I systems, respectively. PCC, Pearson correlation coefficients; Dcat, depth of organic cation in metal-halogen substrate; Hcat height of organic cation; \({L}_{{{{\rm{BX}}}}}^{{{{\rm{v}}}}}\), vertical B-X bond length; \({L}_{{{{\rm{BX}}}}}^{{{{\rm{h}}}}}\), horizontal B-X bond length; ∠BXB, B-X-B bond angle; H height of metal-halogen substrate; ∠γ, lattice angle in plane. c The partial charge densities at the CBM and VBM for (Guanidinium)2PbI4, (Propylammonium)2PbI4, and (Butylammonium)2CdI4. d The band gap change versus B-X-B angle for (Propylammonium)2PbI4. e The band gap change versus vertical B-X bond length for (Butylammonium)2CdI4. f, g The schematic energy level diagrams of (Propylammonium)2PbI4 and (Butylammonium)2CdI4, respectively. The red arrow indicates the main change in the energy level influenced by the B-X-B bond angle or the vertical B–X bond length, resulting in band gap changes.
