Table 1. Predicted Band Gaps, (0/−) and (+/0) Transitions of STEs, (+/0) Transitions of Halogen Vacancies VX (Equatorial, eq; Apical, ap), and Calculated PL Emission Energies of STE and VXa.
| Phase | TIL/eV | PL emission theory/eV | PL emission experiments/eV |
|---|---|---|---|
| PEA2SnI4 (Eg = 2.26 eV) | |||
| STE | |||
| VI eq | (+/0)/1.42 | 0.82 | 0.9 |
| VI ap | (+/0)/1.84 | 1.75 | 1.7 |
| PEA2PbI4 (Eg = 2.58 eV) | |||
| STE | |||
| VI eq | (+/0)/1.94 | 1.27 | (1.7) |
| VI ap | (+/0)/2.07 | 1.97 | 1.95 |
| PEA2PbBr4 (Eg = 3.26 eV) | |||
| STE | (0/−)/3.48 | 2.19 | 2.3 |
| (+/0)/0.05b | |||
| VBr eq | (+/0)/2.56 | 1.78 | 1.75 |
| VBr ap | (+/0)/2.93 | 1.73 | |
| PEA2PbCl4 (Eg = 3.91 eV) | |||
| STE | (0/−)/3.88 | 1.89 | 2 |
| (+/0)/0.12b | |||
| VCl eq | (+/0)/2.89 | 1.97 | |
| VCl ap | (+/0)/3.29 | 1.85 | |
a
All values were calculated at the PBE0 level by correcting for SOC (see Computational Details). In the last column the experimentally observed transitions for the four perovskites are reported for comparison.
b
The (+/0) transitions associated with the self-trapping of the hole are calculated at the PBE0 without SOC corrections, due to the limited influence of SOC on the VB.