Investigations of the structural, optoelectronic and band alignment properties of Cu2ZnSnS4 prepared by hot-injection method towards low-cost photovoltaic applications

Cu2ZnSnS4 is a promising, versatile and inexpensive quaternary semiconductor with suitable optoelectronic properties for solar energy conversion. In this work, we report the synthesis of CZTS nanocrystals (NCs) using low-cost homemade hot-injection method. Oleylamine was used as both the binder and stabilizer for the CZTS NCs during the growth process. Detailed investigation of the influence of sulphur concentration and reaction temperature on the structural, stoichiometric, morphological, and optoelectronic attributes of CZTS NCs was carried out. The XRD, Raman, and TEM measurements confirm the formation of phase-pure tetragonal kesterite CZTS NCs. The synthesized CZTS NCs exhibit particle sizes in the range of 15-30 nm and display strong optical absorption in the visible region. The nearly optimal chemical composition of the CZTS NCs was confirmed by energy dispersive X-ray spectroscopy. UV -Visible spectroscopy and electrochemical measurements predict the band gap of the CZTS NCs in the range of 1.3-1.6 eV, which is very close to the optimum values for the fabrication of single junction solar cells. The estimated conduction band offset (CBO) and valence band offset (VBO) of the CZTS-3M/CdS heterostructure are predicted as 0.11 and 0.98 eV, respectively, whereas for CZTS-225 degrees C/CdS heterostructure, CBO and VBO are 0.10 and 1.0 eV, respectively. The small conduction band offset measured at the CZTS/CdS interface are encouraging characteristics for the carrier transport and the deeper understating of band alignment and interface properties provides a hopeful approach for designing higher efficiency and more efficient carrier separation in CZTS solar cells. (C) 2020 The Authors. Published by Elsevier B.V.

Automated summary

Cu2ZnSnS4 is a promising and versatile quaternary semiconductor for solar energy conversion, with CZTS nanocrystals synthesized using a homemade hot-injection method showing phase-pure tetragonal kesterite structure and optimal optical properties. The small conduction band offset at the CZTS/CdS interface is advantageous for carrier transport, and a deeper understanding of band alignment and interface properties could lead to improved efficiency in CZTS solar cells.