Crystal system: unknown
| Band gap (fundamental), eV |
|---|
Starting materials: PbO, HI, H3PO2, butylamine
Product: spin-coated thin film, high crystallinity
Description: For BA2PbI4 (I): First step: BAPbI4 single crystal flakes synthesized as follows: Slow-cooling in HI method: 2.232g (10 mmol) of PbO dissolved in glass vial containing 10 mL of HI and 1.7 mL of H3PO2. Brought to near-boiling temperature. 10 mmol of the organic amine mixed with 5 mL HI, cooled in an ice bath. For BA2PbI4 (I), solution was cooled to ~80 deg C, upon which crystals began to form and left undisturbed for three days. Afterwards, crystals were slowly cooled to room temperature (rate: 2 deg C/hr). Some crystallites in the film were found in the RT (I) phase and others found in the low-temperature (II) phase. Crystals were then washed thrice with diethyl ether and dried under a vacuum. Second step (thin film formation): Flakes were dissolved in 4:1 DMF:DMSO solvent mixture, stirred for 30 minutes. Substrate: quartz substrate with 120 nm gold layer of interdigitated fingers. Precursor solution (0.05-0.1 molar) pipetted onto substrate and then spun at 4000 rpm for 30 seconds, targeting film thickness of 80-300nm. Film was solvent-annealed, then enclosed with 2mL dH2O.
Method: Electroabsorption
Description: Films were spin-coated onto interdigitated Au electrode array - 45 micron distance between opposing fingers. Samples mounted in cryostat with Cu wires soldered to opposing electrode stripes. Xe lamp light spectrally filtered, focused on sample and subsequently on UV-enhanced Si photodiode detector. Sample transmission, substrate transmission, and sample electrotransmission were collected in independent scans.Absorbance and electroabsorbance were then calculated from the respective transmissions. The fundamental gap is determined by the crossover point of absorption curves measured under different electric fields in the fundamental band gap region.
Comment: Significantly more detail in paper.
Crystal system: unknown
| Band gap (fundamental), eV |
|---|
Starting materials: PbO, HI, H3PO2, butylamine
Product: spin-coated thin film, high crystallinity
Description: For BA2PbI4 (II): First step: BAPbI4 single crystal flakes synthesized as follows: Slow-cooling in HI method: 2.232g (10 mmol) of PbO dissolved in glass vial containing 10 mL of HI and 1.7 mL of H3PO2. Brought to near-boiling temperature. 10 mmol of the organic amine mixed with 5 mL HI, cooled in an ice bath. Solutions were mixed and heated, then cooled to room temperature, upon which single crystal flakes form. Crystals were then washed thrice with diethyl ether and dried under a vacuum. Second step (thin film formation): Flakes were dissolved in 4:1 DMF:DMSO solvent mixture, stirred for 30 minutes. Substrate: quartz substrate with 120 nm gold layer of interdigitated fingers. Precursor solution (0.05-0.1 molar) pipetted onto substrate and then spun at 4000 rpm for 30 seconds, targeting film thickness of 80-300nm. Film was solvent-annealed, then enclosed with 2mL dH2O.
Method: Electroabsorption
Description: Films were spin-coated onto interdigitated Au electrode array - 45 micron distance between opposing fingers. Samples mounted in cryostat with Cu wires soldered to opposing electrode stripes. Xe lamp light spectrally filtered, focused on sample and subsequently on UV-enhanced Si photodiode detector. Sample transmission, substrate transmission, and sample electrotransmission were collected in independent scans.Absorbance and electroabsorbance were then calculated from the respective transmissions. The fundamental gap is determined by the crossover point of absorption curves measured under different electric fields in the fundamental band gap region.
Comment: Significantly more detail in paper.