Two-step spin-coating of vacancy-ordered double perovskites enables growth of thin films for electronic devices

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-charg..., 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)
GIWA..., # Two-step spin-coating of vacancy-ordered double perovskites enables growth of thin films for electronic devices

Dataset DOI: [10.5061/dryad.qnk98sfv0](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...,