Uniform Sb₂S₃optical coatings by chemical spray method

Abstract

Antimony sulfide (Sb2S3), an environmentally benign material, has been prepared by various deposition methods for use as a solar absorber due to its direct band gap of ≈1.7 eV and high absorption coefficient in the visible light spectrum (1.8 × 105 cm−1 at 450 nm). Rapid, scalable, economically viable and controllable in-air growth of continuous, uniform, polycrystalline Sb2S3 absorber layers has not yet been accomplished. This could be achieved with chemical spray pyrolysis, a robust chemical method for deposition of thin films. We applied a two-stage process to produce continuous Sb2S3 optical coatings with uniform thickness. First, amorphous Sb2S3 layers, likely forming by 3D Volmer–Weber island growth through a molten phase reaction between SbCl3 and SC(NH2)2, were deposited in air on a glass/ITO/TiO2 substrate by ultrasonic spraying of methanolic Sb/S 1:3 molar ratio solution at 200–210 °C. Second, we produced polycrystalline uniform films of Sb2S3 (E g 1.8 eV) with a post-deposition thermal treatment of amorphous Sb2S3 layers in vacuum at 170 °C, <4 × 10−6 Torr for 5 minutes. The effects of the deposition temperature, the precursor molar ratio and the thermal treatment temperature on the Sb2S3 layers were investigated using Raman spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and UV–vis–NIR spectroscopy. We demonstrated that Sb2S3 optical coatings with controllable structure, morphology and optical properties can be deposited by ultrasonic spray pyrolysis in air by tuning of the deposition temperature, the Sb/S precursor molar ratio in the spray solution, and the post-deposition treatment temperature.

Semitransparent Sb2S3 thin film solar cells by ultrasonic spray pyrolysis for use in solar windows

“…The substrate coverage of Sb 2 S 3 layers on a glass/ITO/TiO 2 substrate, annealed in vacuum, depends on the quantity of Sb 2 S 3 deposited by USP [46]. Thinner (≤70 nm) Sb 2 S 3 layers contain pin-holes (Fig.…”

“…1), which are characteristic of amorphous Sb 2 S 3 [28,46]. After vacuum annealing, characteristic narrower bands of Sb 2 S 3 are detected, which is an expected result when crystalline Sb 2 S 3 is formed [28,46,49]. No traces of additional phases were detected by either XRD or Raman in any glass/ITO/TiO 2 /Sb 2 S 3 samples.…”

“…ITO covered (25 Ω sq −1 , ZSW) soda-lime glass substrates were cleaned with deionized water, ethanol, deionized water, H 2 SO 4 (1% w/w), and rinsed with deionized water before drying at 105 °C in air. Then, a dense, compact TiO 2 layer was grown on glass/ITO by ultrasonic spray pyrolysis in air from 0.1 M titanium tetraisopropoxide (98% v/v) and 0.4 M acetylacetone (99% v/v) dissolved in ethanol (96.6% v/v) according to a previously published procedure [28,46,70]. After deposition, the glass/ITO/TiO 2 stack was annealed at 450 °C for 30 min in air to form anatase.…”

“…Previously, we observed that the moderate photocurrent density and PCE (of 1.9%) in solar cells based on Sb 2 S 3 layers grown by USP was due to a discontinuity of the Sb 2 S 3 layer [28]. In our recent study, we showed that the discontinuity of Sb 2 S 3 films grown by USP, and likely other chemical methods, is a result of 3D island growth [46]. We demonstrated that by adapting a two-step sequence, whereby amorphous Sb 2 S 3 layers are first deposited by USP and then crystallized by thermal annealing, compact Sb 2 S 3 thin films with uniform thickness can be fabricated [46].…”

“…In our recent study, we showed that the discontinuity of Sb 2 S 3 films grown by USP, and likely other chemical methods, is a result of 3D island growth [46]. We demonstrated that by adapting a two-step sequence, whereby amorphous Sb 2 S 3 layers are first deposited by USP and then crystallized by thermal annealing, compact Sb 2 S 3 thin films with uniform thickness can be fabricated [46]. Similarly, a two-step procedure to grow compact Sb 2 S 3 thin films has become common practice for many deposition techniques [18–20 27,29,31,35,47].…”