Two-step spin-coating of vacancy-ordered double perovskites enables growth of thin films for electronic devices
Data files
Jul 23, 2025 version files 345.91 MB
-
Cs2TeBr6_Paper_Data.zip
345.90 MB
-
README.md
11.98 KB
Abstract
Vacancy-ordered double perovskites (VODPs), such as Cs2TeX6 (X = Cl, Br, I), are lead-free alternatives to conventional metal-halide perovskites (MHPs). One limitation of VODPs is the lack of processes to form thin films relevant for physical characterization and electronic devices. A two-step spin-coating method was developed for synthesizing high-quality films of Cs2TeBr6. Independently depositing CsBr and TeBr4 enables high precursor concentration and control over crystallization dynamics. By optimizing spin-coating parameters, conversion of precursors to phase pure films was observed using structural and surface characterization methods. The growth of mixed-halide systems was investigated using alternative salts including CsCl and CsI. Formation of halide alloys was found to depend on the existence of routes to byproducts. Lastly, single carrier diodes of Cs2TeBr6 were designed following valence band characterization with photoelectron spectroscopy. Temperature-dependent space-charge-limited current measurements revealed that transport occurs by hopping and the hole mobility is 3.2 x 10-5 cm2 V-1 s-1 near room temperature. The insights from the 2-step procedure provide a pathway towards making semiconducting devices from VODPs.
Dataset DOI: 10.5061/dryad.qnk98sfv0
Cs₂TeBr₆ films were characterized with a variety of techniques. Powder X-ray diffraction (PXRD) was performed with a Panalytical Empyrean Powder Diffractometer to confirm phase purity. Grazing incidence wide-angle X-ray scattering (GIWAXS) was conducted at the Stanford Synchrotron Radiation Lightsource (SSRL) on beamline 11-3 to assess phase purity and film crystallinity. Optical properties were evaluated using a Shimadzu UV3600 UV-Vis-NIR Spectrometer for diffuse reflectance and band gap determination, and photoluminescence spectra were collected with a spectrometer and visible CCD detector under 405 nm laser excitation. Film morphology was examined using a Thermo Scientific Apreo C LoVac scanning electron microscope (SEM). Ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) were performed on a Thermo Scientific ESCALAB Xi+ XPS Microprobe to probe electronic structure and surface composition. Device performance was evaluated with current-voltage (J–V) measurements using a LakeShore Cryogenic Probe Station and a Keithley 2400 SourceMeter.
Cs2TeBr6_Paper_Data.zip – Files and Folders
Figure 2
SEM images of TeBr4 and Cs2TeBr6 films made via two-step spin-coating procedure and drop-casting. The drop-cast film was made by dropping 200 μL of 0.125 M Cs2TeBr6 solution onto a quartz substrate at 170 °C. 50 μL of toluene was deposited in tandem as an anti-solvent. The two-step spin-coated film was made by spinning 50 μL of 1 M TeBr4 at 2000 rpm followed by 50 μL of 1 M CsBr deposited dynamically at 2000 rpm. PXRD patterns for the spin-coated Cs2TeBr6 film and the drop-cast Cs2TeBr6 film.
"Cs2TeBr6 Dropcast – PXRD.csv"
- Measurement conditions of PXRD experiment
- 2θ angle (°) and intensity raw data
"Cs2TeBr6 Dropcast – SEM.tif"
- Raw TIFF file of SEM image
"Cs2TeBr6 Spincoat – PXRD.csv"
- Measurement conditions of PXRD experiment
- 2θ angle (°) and intensity raw data
"Cs2TeBr6 Spincoat – SEM.tif"
"TeBr4 Spincoat – SEM.tif"
- Raw TIFF files of SEM images
Figure 3
Azimuthally integrated GIWAXS data collected at a 3° incidence angle of Cs2TeBr6 films made by depositing 0.5 M, 1 M, and 1.5 M CsBr solution in two-step spin-coating procedure. The TeBr4 pattern is included for peak assignment. SEM images of Cs2TeBr6films made with varying CsBr deposition spin-speeds.
"0.5 M CsBr Detector Image – GIWAXS.tif"
- Raw TIFF file of GIWAXS detector image
"0.5 M CsBr Integrated Signal – GIWAXS.csv"
- GIWAXS data after making geometric corrections with Nika and integrating with WAXStools
- q (A⁻¹) and integrated intensity data
"1 M CsBr Detector Image – GIWAXS.tif"
- Raw TIFF file of GIWAXS detector image
"1 M CsBr Integrated Signal – GIWAXS.csv"
- GIWAXS data after making geometric corrections with Nika and integrating with WAXStools
- q (A⁻¹) and integrated intensity data
"1.5 M CsBr Detector Image – GIWAXS.tif"
- Raw TIFF file of GIWAXS detector image
"1.5 M CsBr Integrated Signal – GIWAXS.csv"
- GIWAXS data after making geometric corrections with Nika and integrating with WAXStools
- q (A⁻¹) and integrated intensity data
"2000 rpm Second Layer – SEM.tif"
"4000 rpm Second Layer – SEM.csv"
"6000 rpm Second Layer – SEM.csv"
"8000 rpm Second Layer – SEM.csv"
- Raw TIFF files of SEM images
"TeBr4 Detector Image – GIWAXS.tif"
- Raw TIFF file of GIWAXS detector image
"TeBr4 Integrated Signal – GIWAXS.csv"
- GIWAXS data after making geometric corrections with Nika and integrating with WAXStools
- q (A⁻¹) and integrated intensity data
Figure 4
UV-Vis reflectance data for films made by depositing CsCl and CsI solutions of varying concentrations. Azimuthally integrated GIWAXS data of films made with increasing CsCl concentration. Azimuthally integrated GIWAXS data of films made with increasing CsI concentration. Photoluminescence of films made with increasing CsI concentration, excited at 405 nm.
"0.5 M CsCl – UV-Vis.csv"
"1 M CsCl – UV-Vis.csv"
"1.5 M CsCl – UV-Vis.csv"
- Wavelength (nm) and reflectance % raw data
"0.5 M CsCl – PL.csv"
"1 M CsCl – PL.csv"
"1.5 M CsCl – PL.csv"
- Wavelength (nm) and emission intensity
"0.5 M CsCl Integrated Signal – GIWAXS.csv"
"0.5 M CsI Integrated Signal – GIWAXS.csv"
"1 M CsCl Integrated Signal – GIWAXS.csv"
"1 M CsI Integrated Signal – GIWAXS.csv"
"1.5 M CsCl Integrated Signal – GIWAXS.csv"
"1.5 M CsI Integrated Signal – GIWAXS.csv"
"0.5 M CsCl Detector Image – GIWAXS.csv"
- GIWAXS data after making geometric corrections with Nika and integrating with WAXStools
- q (A⁻¹) and integrated intensity data
"0.5 M CsI Detector Image – GIWAXS.tif"
"1 M CsCl Detector Image – GIWAXS.tif"
"1 M CsI Detector Image – GIWAXS.tif"
"1.5 M CsCl Detector Image – GIWAXS.tif"
"1.5 M CsI Detector Image – GIWAXS.tif"
- Raw TIFF files of GIWAXS detector images
Figure 5
J–V data for a Cs2TeBr6 device at various temperatures used to extract hole mobility. "Forward Bias" and "Reverse Bias" are at 280 K.
"Forward Bias – SCLC.csv"
"Reverse Bias – SCLC.csv"
"280 K Mobility Fit – SCLC.csv"
"270 K Mobility Fit – SCLC.csv"
"260 K Mobility Fit – SCLC.csv"
"250 K Mobility Fit – SCLC.csv"
"240 K Mobility Fit – SCLC.csv"
"230 K Mobility Fit – SCLC.csv"
"220 K Mobility Fit – SCLC.csv"
- Current (A) and voltage (V) raw data collected with Keithley 2400
- Data from 0 V to 0.5 V was fit to Ohm's law to extract the shunt resistance, which was then used to subtract shunt background current from the raw data to successfully fit SCLC curve
Figure S1
Cross-sectional images of a Cs2TeBr6 film made by spinning TeBr4 at 4000 rpm followed by CsBr at 2000 rpm. The film was grown on a silicon substrate which was broken in half to view the cross-section at the middle of the film.
"Film Cross-Section – SEM.tif"
"Film Cross-Section Zoomed-In – SEM.tif"
- Raw TIFF file of SEM images
Figure S2
Time evolution of emission from CsPbBr3 and Cs2TeCl6 films made via a two-step deposition process. CsX solution was deposited at t = 0 s. Additional emission features centered around 2.75 eV and 1.60 eV are likely a measurement artifact intensified because of the relatively low PL emission intensity.
"Cs2TeCl6 – In-situ PL.csv"
"CsPbBr3 – In-situ PL.csv"
- Folder of wavelength (nm) and emission intensity raw data files
- Number in the file name indicates the order of collection, with each data point captured with an integration time of 0.5 s
"Cs2TeCl6 Peak Locations – In-situ PL.csv"
"CsPbBr3 Peak Locations – In-situ PL.csv"
- Time (s), peak position (eV), and emission intensity from Gaussian fit of raw emission data
Figure S3
GIWAXS images of Cs2TeBr6 films made with 0.5 M, 1 M, and 1.5 M CsBr solution.
"0.5 M CsBr Detector Image – GIWAXS.tif"
"1 M CsBr Detector Image – GIWAXS.tif"
"1.5 M CsBr Detector Image – GIWAXS.tif"
- Raw TIFF files of GIWAXS detector images
Figure S4
Azimuthally integrated GIWAXS data of Cs2TeBr6 films acquired with varying grazing-incidence angle. The pink shaded region marks the most prominent TeBr4 reflection. Films were made by spinning 50 uL of 1 M TeBr4 at 2000 rpm followed by 50 uL of 1 M CsBr deposited dynamically at 2000 rpm.
"0.2° Detector Image – GIWAXS.tif"
"0.5° Detector Image – GIWAXS.tif"
"1° Detector Image – GIWAXS.tif"
"2° Detector Image – GIWAXS.tif"
- Raw TIFF files of GIWAXS detector images
"0.2° Integrated Signal – GIWAXS.csv"
"0.5° Integrated Signal – GIWAXS.csv"
"1° Integrated Signal – GIWAXS.csv"
"2° Integrated Signal – GIWAXS.csv"
- GIWAXS data after making geometric corrections with Nika and integrating with WAXStools
- q (A⁻¹) and integrated intensity data
Figure S5
XPS scans of a Cs2TeBr6 film in binding energy regions for cesium, tellurium, and bromide. The film was made by spin-coating 1 M TeBr4 at 2000 rpm followed by 1 M CsBr at 2000 rpm.
"Bromine Scan – XPS.csv"
"Cesium Scan – XPS.csv"
"Tellurium Scan – XPS.csv"
- Kinetic energy (eV) and intensity raw XPS data
Figure S6
XPS scans of a TeBr4 film in binding energy regions for tellurium and bromide.
"Bromine Scan – XPS.csv"
"Tellurium Scan – XPS.csv"
- Kinetic energy (eV) and intensity raw XPS data
Figure S8
Azimuthally integrated GIWAXS data collected at a 3° incidence angle of Cs2TeBr6 film made by depositing both layers at 6000 rpm.
"6000 rpm Detector Image – GIWAXS.tif"
- Raw TIFF file of GIWAXS detector image
"6000 rpm Integrated Signal – GIWAXS.csv"
- GIWAXS data after making geometric corrections with Nika and integrating with WAXStools
- q (A⁻¹) and integrated intensity data
Figure S9
SEM images of films made by varying the spin speed of both the first TeBr4 layer and the second CsBr layer.
"2000 rpm First Layer 2000 rpm Second Layer – SEM.tif"
"2000 rpm First Layer 4000 rpm Second Layer – SEM.tif"
"2000 rpm First Layer 8000 rpm Second Layer – SEM.tif"
"4000 rpm First Layer 2000 rpm Second Layer – SEM.tif"
"4000 rpm First Layer 4000 rpm Second Layer – SEM.tif"
"4000 rpm First Layer 8000 rpm Second Layer – SEM.tif"
- Raw TIFF files of SEM images
Figure S10
PXRD patterns for Cs2TeCl6 and Cs2TeI6 formed via two-step spin-coating.
"Cs2TeCl6 – PXRD.csv"
"Cs2TeI6 – PXRD.csv"
- Measurement conditions of PXRD experiment
- 2θ angle (°) and intensity raw data
Figure S11
XPS scan of a film made by spin-coating 1 M TeBr4 and 1 M CsCl in the binding energy region for chlorine. There are no photoemission peaks in the spectrum.
"Chlorine Scan – XPS.csv"
- Kinetic energy (eV) and intensity raw XPS data
Figure S12
Azimuthally integrated GIWAXS data collected at a 3° incidence angle of a film made by depositing CsI on top of TeBr4 via a two-step deposition.
"0.5 M TeBr4 + 1 M CsI Detector Image – GIWAXS.tif"
- Raw TIFF file of GIWAXS detector image
"0.5 M TeBr4 + 1 M CsI Integrated Signal – GIWAXS.csv"
- GIWAXS data after making geometric corrections with Nika and integrating with WAXStools
- q (A⁻¹) and integrated intensity data
Figure S13
UPS spectrum of Cs2TeBr6 film with fiGed energy onset and cutoff.
"Cs2TeBr6 Valence Band – UPS.csv"
- Kinetic energy (eV) and intensity raw UPS data
Figure S14
XPS scans of a Cs2TeBr6 device in binding energy regions for cesium, tellurium, and bromide. The film was made by spin-coating 1 M TeBr4 at 4000 rpm followed by 1.5 M CsBr at 2000 rpm.
"Bromine Scan – XPS.csv"
"Cesium Scan – XPS.csv"
"Tellurium Scan – XPS.csv"
- Kinetic energy (eV) and intensity raw XPS data
Figure S15
J-V curve for Cs2TeBr6 SCLC diode held at 280 K used to extract hole mobility value.
"280 K Mobility Fit – SCLC.csv"
- Current (A) and voltage (V) raw data collected with Keithley 2400
- Data from 0 V to 0.5 V was fit to Ohm's law to extract the shunt resistance, which was then used to subtract shunt background current from the raw data to successfully fit SCLC curve
Figure S16
J-V curves for Cs2TeBr6 SCLC diode acquired at various temperatures to extract hole mobility value.
"280 K Mobility Fit – SCLC.csv"
"270 K Mobility Fit – SCLC.csv"
"260 K Mobility Fit – SCLC.csv"
"250 K Mobility Fit – SCLC.csv"
"240 K Mobility Fit – SCLC.csv"
"230 K Mobility Fit – SCLC.csv"
"220 K Mobility Fit – SCLC.csv"
- Current (A) and voltage (V) raw data collected with Keithley 2400
- Data from 0 V to 0.5 V was fit to Ohm's law to extract the shunt resistance, which was then used to subtract shunt background current from the raw data to successfully fit SCLC curve
Powder X-Ray Diffraction
Powder X-ray diffraction patterns were collected with a Panalytical Empyrean Powder Diffractometer in reflection mode. Cu Kα1 was used as the X-ray radiation source with an accelerating voltage of 45 kV and beam current of 40 mA. Scans were performed from 2θ = 3° to 2θ = 60° with a step size of 0.04° and step time of 40 ms.
UV-Vis
A Shimadzu UV3600 UV-Vis-NIR Spectrometer was used to collect diffuse reflectance spectra. Scans were performed from 300 to 900 nm with a step size of 0.5 nm. Reflectance data was converted to absorbance with the Kubelka-Munk transform. Tauc plots for indirect band gap materials were generated to determine the band gap with a linear fit of the absorption edge.
Photoluminescence
Emission spectra was collected in reflectance mode with a 430 nm long pass filter, spectrometer, and visible CCD detector. Samples were excited at 405 nm with a continuous wave laser diode.
Grazing incidence wide-angle X-ray scattering (GIWAXS)
GIWAXS experiments were performed at Stanford Synchrotron Radiation Lightsource (SSRL) on beam line 11-3, which has a fixed energy of 12.7 keV and is equipped with a two-dimensional Rayonix MX225 CCD area detector. Lanthanum hexaboride (LaB6) was used to refine the beam center and sample-to-detector distance. Data was collected with an incidence angle of 3° to access a large range in q. Geometric corrections to the raw images were made using Nika. Data was azimuthally integrated with WAXStools.
Scanning Electron Microscopy (SEM)
SEM images were collected with a Thermo Scientific Apreo C LoVac SEM. Films were mounted onto SEM stubs with double-sided copper tape and imaged with accelerating voltages of 5.00 kV and beam currents of 0.40 nA.
Ultraviolet and X-ray Photoelectron Spectroscopy
Ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) experiments were performed with a Thermo Scientific ESCALAB Xi+ XPS Microprobe. For UPS experiments, before film casting, 20 nm of chromium followed by 90 nm of gold were deposited by thermal evaporation onto quartz substrates so that films did not experience charging. Cs2TeBr6 films were cast with an initial TeBr4 layer spun at 8000 rpm so that the film was sufficiently thin to prevent charging issues. Nickel tape was adhered to the surface of the film and wrapped around the edge of the substrate to further assist with charge dissipation. A helium I radiation source was used, performing 5 scans with a pass energy of 1.5 eV, dwell time of 150 ms, and energy step size of 0.05 eV. Additional low energy scans were conducted with electron charge compensation to ensure that sample charging didn't alter the onset, aligning with data collected without compensation. A corrected helium I satellite line background was subtracted using CasaXPS. For XPS experiments, X-rays are generated with a monochromated aluminum anode (1486.7 eV). Scans were performed with a pass energy of 100 eV, dwell time of 20 ms, and energy step size of 0.5 eV. Charge compensation was applied, and charge shift was accounted for by calibrating to trace oxygen photoemission at 531 eV. Thermo Scientific Avantage Data System was used to fit peaks with a Smart background and quantify atomic percentages.
Device Fabrication and Testing
Devices were tested with a LakeShore Cryogenic Vacuum Probe Station and Keithley 2400 SourceMeter. Current-voltage scans were performed with a step size of 0.05 V.