Structural and optical analysis of single phase CuInS₂ nanocrystals for solar cell applications

Abstract

Nanostructured phase pure CuInS2 particles have been successfully synthesized by solid state melt growth method. The crystallographic structure, morphological, chemical composition and optical properties of synthesized sample have been characterized by various analytical techniques, includes X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray (EDAX), UV–vis–NIR diffuse reflectance spectroscopy and photoluminescence spectroscopy. From the XRD spectra chalcopyrite structure of CuInS2 sample with phase pure nano particles is confirmed. Annealing promotes the grain size and crystallinity of the CuInS2 sample and is clearly indicated by XRD analysis. The optical band gap energy of CuInS2 sample is calculated to be 2.61 eV, which has also been confirmed by photoluminescence spectroscopy. SEM micrograph shows that the CuInS2 sample is composed of particles ranges from 25–50 nm in size. Annealed sample confirms the increase of particle size up to 85 nm. Compositional stability of CuInS2 phase pure nano particles have been studied by thermo gravimetric analysis. The effect of annealing temperatures on the structural and morphological properties of CuInS2 nanocrystals synthesized by solid state reactions has also been studied in this report.

Sonochemically Synthesized Quantum Nanocrystals of Cubic CuInS2: Evidence for Multifractal Surface Morphology, Size-Dependent Structure, and Particle Size Distribution

“…Numerous papers have also been devoted to the investigation of the physical and chemical properties of CuInS 2 . However, when it comes to CuInS 2 NCs, or, in general, low-dimensional CuInS 2 of either zinc blende (cubic) or wurtzite (hexagonal) structural type, the number of studies becomes rather limited. ,− ,− According to the literature data, these films have generally been prepared by conventional growth methods such as sputtering, evaporation, and chemical vapor deposition, while synthetic routes to nanocrystals have often been realized under harsh conditions (such as high vacuum and high temperature). This increases the cost of synthesis processes, and at the same time, they are hardly scaled up to produce large amounts of the material on an industrial scale.…”

Solution-Processed in Situ Growth of CuInS2 Nanoparticle Films for Efficient Planar Heterojunction Solar Cells with a Dual Nature of Charge Generation

“…21,22 The average size (D) of the CuInS 2 nanocrystals is calculated to be ∼3.2 nm by the Scherrer formula D = Kλ(B cos θ) −1 , where K is a constant (0.9), λ is the X-ray wavelength (1.54056 Å), B is the full width half-maximum (in radians), and θ is the Bragg angle of the (112) peak. 23,24 We also observed the TiO 2 /CdS/CuInS 2 films with the annealing temperature (T a ) of 250 and 300 °C. As shown in Figure S2, an increase in T a imposes a slight effect on the resulting CuInS 2 nanoparticle size but leads to the intensified XRD peaks of CuInS 2 suggesting a higher T a for a higher CuInS 2 crystallinity; however, Raman data showed that a binary chalcogenide (Cu x S y ) impurity appeared at T a = 300 °C.…”

“…The broad absorption extending from the ultraviolet to near-infrared regions indicates actually a broad size distribution of CuInS 2 nanoparticles in the CuInS 2 layer, including quantum dots with a size smaller than Bohr exciton radius (∼4.1 nm) 11,22,23 and nanoparticles with a diameter larger than 8 nm. 15,21,24,27 Noticeably, the annealing temperature T a almost imposed no remarkable influence on the CuInS 2 film absorption property, and the very comparable absorbance was observed in the 200 nm-thick CuInS 2 layers prepared at T a = 250−300 °C (Figure S5a).…”

“…As shown in Figure a, the TiO 2 film exhibits a band gap ( E g ) absorption onset at 386 nm ( E g = 3.21 eV), while the TiO 2 /CdS film additionally shows the CdS absorption in the form of a shoulder peak at 400–530 nm. , The TiO 2 /CdS/CuInS 2 film is characterized by a broad shoulder with a tail in the long-wavelength direction typically up to the near-infrared region due to CuInS 2 absorption. The broad absorption extending from the ultraviolet to near-infrared regions indicates actually a broad size distribution of CuInS 2 nanoparticles in the CuInS 2 layer, including quantum dots with a size smaller than Bohr exciton radius (∼4.1 nm) ,, and nanoparticles with a diameter larger than 8 nm. ,,, Noticeably, the annealing temperature T a almost imposed no remarkable influence on the CuInS 2 film absorption property, and the very comparable absorbance was observed in the 200 nm-thick CuInS 2 layers prepared at T a = 250–300 °C (Figure S5a).…”

“…The TiO 2 /CdS/CuInS 2 film exhibits the three diffraction peaks at 27.6°, 46.0°, and 54.7°, which match well the (112), (204)/(220), and (116)/(312) crystal planes of chalcopyrite CuInS 2 (JCPDS 085-1575), respectively. The XRD patterns of CuInS 2 show broad diffraction peaks, indicating the presence of small chalcopyrite CuInS 2 nanocrystals. , The average size ( D ) of the CuInS 2 nanocrystals is calculated to be ∼3.2 nm by the Scherrer formula D = K λ­( B cos θ) −1 , where K is a constant (0.9), λ is the X-ray wavelength (1.54056 Å), B is the full width half-maximum (in radians), and θ is the Bragg angle of the (112) peak. , We also observed the TiO 2 /CdS/CuInS 2 films with the annealing temperature ( T a ) of 250 and 300 °C. As shown in Figure S2, an increase in T a imposes a slight effect on the resulting CuInS 2 nanoparticle size but leads to the intensified XRD peaks of CuInS 2 suggesting a higher T a for a higher CuInS 2 crystallinity; however, Raman data showed that a binary chalcogenide (Cu x S y ) impurity appeared at T a = 300 °C.…”