Structural evolution of chemically deposited binary stacks of Sb ₂ S ₃ ‐CuS to phase‐pure CuSbS ₂ thin films and evaluation of device parameters of CuSbS ₂ /CdS heterojunction

Abstract

Copper-based chalcogenide ternary compounds are promising materials to be used as absorber layer in solar cells. In this work, we have reported the preparation of copper antimony sulfide (CAS) thin films by annealing chemically deposited multi-stack of Sb 2 S 3 -CuS and the effect of thickness ratio between two binary sulfides on the formation of different crystalline phases of Cu-Sb-S system. A series of multilayer structure was prepared with different thickness of CuS in order to study the effect of copper concentration on the structural, morphological, optical, and electrical properties of the resulting Cu x Sb 1-x S y films. The CAS films were characterized by several techniques such as X-ray diffraction, Raman scattering, UV-visible spectroscopy, atomic force microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, andHall effect measurements to evaluate their physical properties. The formation of either pure chalcostibite (CuSbS 2 ) or mixed ternary phases containing chalcostibite, famatinite (Cu 3 SbS 4 ), and tetrahedrite (Cu 12 Sb 4 S 13 ) were detected depending on the thickness ratio of Sb 2 S 3 and CuS. Chalcostibite films revealed desired optical and electrical values. Finally, solar cell was fabricated using the heterostructure FTO/CdS/CuSbS 2 /Ag and characterized by currentvoltage, capacitance-voltage, and impedance-spectroscopy measurements achieving a promising~0.8% efficiency with V OC = 0.484 V, J SC = 5.97 mA/cm 2 , and FF =27.34%. Impedance measurements revealed a low series resistance in the optimal solar cell, as a result, an increment in open circuit voltage. Novelty StatementThe novelty of this work is the fabrication of CuSbS 2 thin films by tuning the thickness ratio of binary sulfides in Sb 2 S 3 -CuS stack followed by proper thermal annealing. Furthermore, impedance spectroscopic studies of CuSbS 2 solar cell are still lacking; the present study may provide important physical insight to understand the device performance and possibilities toward any further improvement.

Chemical vapor reaction synthesis and photoelectronic properties of CuS and Cu3SbS4 thin films

“…The Raman spectrum of the film prepared at 350 °C, show the 127.0, 246.4, 312.7, 342.0, 468.6 cm −1 modes. The 246.4, 312.7, and 342.0 cm −1 belong to the Cu 3 SbS 4 phase, while the broad peak at 127.0, 246.4 cm −1 and the peak at 468.4 cm −1 show the film is not pure Cu 3 SbS 4 at 350 °C [40,41], which is in good agreement with the XRD results, and the common structure of Cu 3 SbS 4 was shown in figure 2(d).…”

Sulfurization of Electrodeposited Sb/Cu Precursors for CuSbS2: Potential Absorber Materials for Thin-Film Solar Cells

“…The highest efficiency of CuSbS 2 thin films fabricated via electrodeposition is 3.13% (Septina et al, 2014), which is far lower than the maximum theoretical conversion efficiency of 22.9% (SLME) (Yu et al, 2013). The main factor limiting the further improvement of CuSbS 2 thinfilm solar cells are 1) rough electrodeposited metal precursors lead the thickness and composition distribution to be nonuniform (Yuan et al, 2009;Gao et al, 2020)and 2) secondary phases, such as Sb 2 S 3 , Cu 12 Sb 4 S 13 , and Cu 3 SbS 4 , easily form during annealing (Kang et al, 2018;Pal et al, 2020). Zhang et al (2016) have demonstrated the crystallinity of CuSbS 2 thin films fabricated by electrodepositing Mo/Cu/Sb metal layers followed by sulfurizing in 20% H 2 S + Ar atmosphere for 1 h at 450 °C.…”

“…CuSbS 2 is a direct bandgap material, which can be adjusted between 1.4 and 1.6 eV (Medina-Montes et al, 2018;Pal et al, 2020), and its optical absorption coefficient is greater than 10 5 cm −1 (Vinayakumar et al, 2019). Its grain growth temperature is within 300 °C-450 °C (Yang et al, 2014;Riha et al, 2017), which is lower than those of Cu (In, Ga) Se 2 and Cu 2 ZnSnS 4 .…”