Starting materials: (PEA)2PbBr4 crystals, DMF, glass substrates
Product: Thin film on glass
Description: Dissolve the 2D single crystals into DMF at a concentration 6%∼10% relative to the total weight. Spin-coat at 3000 rpm for 30 s on glass substrates. Anneal in air at 100 °C for 10 min before measurement.
Method: Photoluminescence
Description: The photoluminescence spectra were measured using a Horiba-Jobi-Yvon LabRAM ARAMIS system, with a 325 nm He-Cd laser excitation. The laser beam was collimated and focused through a 40X UV objective onto the sample surface at room temperature. Refer to figure 5.
Starting materials: phenethylammonium bromide (C8H12BrN), lead bromide (PbBr2)
Product: Thin film of (C12H25NH3)2PbBr4
Description: (PEA)Br and PbBr2 made up the target solution in 1:1 DMSO/MEG by volume. They were mechanically mixed until visibly dissolved in solvent, taking about 5 min. In a growth chamber, the solution is cooled to -196°C under vacuum. When frozen, the top layer is removed using an Er:YAG laser (2.94 μm). The laser rasters across the surface to sublimate the MEG, causing the precursor material to be ejected onto the substrate (2 cm × 2 cm of SiO2 glass) spinning 7 cm above. The substrate temperature is approximately 10 °C while in the growth chamber. Deposit time was 4 h. Samples remained in a load lock under turbo vacuum (2 × 10–5 Torr) for an hour afterwards. The annealed films were additionally annealed for 10 min on a hot plate in an N2 environment at 110°.
Method: UV-Vis absorption
Description: PL spectroscopy measurements were taken using a HORIBA Jobin Yvon LabRam ARAMIS system. All films were excited using a 325 HeCd laser source with a 1% filter. Samples were kept in ambient air conditions.