Code: FHI-aims

Level of theory: DFT

Exchange-correlation functional: HSE06

K-point grid: 3×4×4

Level of relativity: atomic ZORA with SOC

Basis set definition: NAO

Geometry used in the calculation

External repositories:

• https://dx.doi.org/10.17172/NOMAD/2020.08.11-1

• Rayan C Duke University

Starting materials: 1-(1-naphthyl) ethylamine (98%, Sigma Aldrich), lead bromide (PbBr2, 99.99%, TCI chemicals) and hydrobromic acid (HBr) (48 wt% in H2O, >99.99%, Sigma Aldrich)

Product: 1-(1-naphthyl)ethylammonium]2PbBr4

Description: To grow rac-NPB perovskite crystals, stoichiometric amounts of PbBr2 (90 mg, 0.24 mmol) and 1-(1-naphthyl) ethylamine (78 µL, 0.48 mmol) were dissolved in aq. HBr (1.0 mL) and methanol (2.4 mL) in a sealed vial at 95 °C. The hot solution was slowly cooled to room temperature (21 °C) over a period of 24 h in a water bath, resulting in the formation of layered flakes of transparent rac-NPB single crystals.

Method: Differential Scanning Calorimetry

Description: Differential Scanning Calorimetry: DSC measurements were performed using a TA Discovery DSC instrument using various ramping rates and temperature ranges (as described in the main text) using a hermetically sealed aluminum pan and lid. Prior to experiments, the DSC setup was calibrated with metallic indium (melting temperature: 156.6 °C; enthalpy of melting: 28.71 J g−1 ), which upon repeating the experiment showed an acceptable temperature offset of 0.2 °C and melting enthalpy offset of 0.04%. Calibration and the above measurement were carried out at a ramp rate of 5 °C min−1 . DSC analyses of crystalline S-NPB and rac-NPB perovskites were carried out by hermetically sealing corresponding crystals (≈5.0 mg) in aluminum pan/lid, and ramping temperature from 25 to 250 °C at a ramp rate of 5 °C min−1.

Starting materials: 1-(1-naphthyl) ethylamine (98%, Sigma Aldrich), lead bromide (PbBr2, 99.99%, TCI chemicals) and hydrobromic acid (HBr) (48 wt% in H2O, >99.99%, Sigma Aldrich)

Product: 1-(1-naphthyl)ethylammonium]2PbBr4

Description: To grow rac-NPB perovskite crystals, stoichiometric amounts of PbBr2 (90 mg, 0.24 mmol) and 1-(1-naphthyl) ethylamine (78 µL, 0.48 mmol) were dissolved in aq. HBr (1.0 mL) and methanol (2.4 mL) in a sealed vial at 95 °C. The hot solution was slowly cooled to room temperature (21 °C) over a period of 24 h in a water bath, resulting in the formation of layered flakes of transparent rac-NPB single crystals.

Method: Thermogravimetric Analysis

Description: Thermogravimetric Analysis: TGA measurements were performed on a TA Q50 instrument using a 5 °C min−1 ramping rate from 25 to 300 °C under nitrogen gas flow (40 mL min−1) with samples (≈4.5 mg) of single crystals of S-NPB and rac-NPB perovskite.