Lambda 950

The transmittance and reflectance of the perovskite films were measured using an optical spectrophotometer (Lambda 950S, Perkin Elmer, Waltham, MA, USA). The band gap of the perovskite films was calculated by Tauc’s plot, which uses the values of absorption coefficient α of the film calculated from the transmittance (T) and reflectance (R) data according to the formula: α = −1/d × ln[(1−R)T]. We used the reflectance data in order to increase accuracy.

The reflectance of the diatomite-based hybrid RCCs in the solar region ( ${\mathrm{R}}_{\mathrm{solar}}$ ) were measured using the UV/VIS/NIR (ultraviolet–visible–near infrared) spectrophotometer (Lambda 950, PerkinElmer Inc., Waltham, MA, USA) with an integrating sphere setup. The transmittance and reflectance spectra of the hybrid RCCs within the atmospheric transparent window region (8–14 μm) were obtained using a Fourier transform infrared spectrometer (Nicolet 6700, Thermo Fisher Scientific Inc., Waltham, MA, USA) equipped with an infrared integrating sphere. The emissivity/absorptivity of the coatings were then calculated as 1—Reflectance—Transmittance. Since the transmittance of all samples is nearly zero, the emissivity spectra in the atmospheric window can essentially be determined by 1—Reflectance.

The morphology of the Ag nanoparticles was observed with a transmission electron microscopy (TEM) (HT770) operating at 80 kV and a scanning electron microscope (SEM) (Hitachi SU-8010) operating at 5.0 kV. The microstructure of the electrodeposited Ag nanoparticles was determined by an X-ray diffraction spectrometer (XRD) (D/Max 2550 pc). The formation efficiency of the Ag nanoparticles was estimated using a thermal gravimetric analyzer (DSCQ1000) through annealing the colloidal solution under the protection of nitrogen. All of the photographs were recorded by a digital camera (Canon EOS750D). SERS measurements were performed on a confocal Raman microscopic system (LabRAM HR Evolution, France). The excitation wavelength was 633 nm generated by an Nd: yttrium-aluminum-garnet laser operating at a power of about 0.25 mW. The accumulation time for the SERS signals was 10 s. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) measurements were operated on a Nicolet 5700 FTIR spectrometer and an Axis Supra XPS spectrometer, respectively. The absorption spectra were obtained using an ultraviolet-visible-near infrared spectrophotometer (PerkinElmer Lambda 950).

The phase and crystallographic structure of the prepared products were characterized by X-ray diffraction on a Bruker D8 Advance X-ray powder diffractometer (XRD) with Cu Kα radiation source (λ = 0.15418 nm). Scanning electron microscopy (SEM) images were acquired using a FEI Nova NanoSEM 450 scanning electron microscope (FEI, Hillsboro, OR, USA). Transmission electron microscopy (TEM) images were performed on a JEOL JEM-2010 electron microscope (JEOL, Akishima-shi, Tokyo, Japan) operating at 200 kV. X-ray photoelectron spectroscopy (XPS) analysis was performed with a Kratos Axis Ultra system using monochromatic Al Kα X-rays (1,486.6 eV). The UV-vis absorption spectra were obtained by using UV-vis Spectrometer (Perkin-Elmer, Lambda 950, Waltham, MA, USA). The simulated crystal structures and wurtzite XRD patterns of CuInS₂ were obtained by using Diamond 3.2 programs.