Influence of Na2S treatment on CZTS/Mo interface in Cu2ZnSnS4 solar cells annealed in sulfur-free atmosphere

Fabrication of Cu2ZnSnS4 Light Absorber Using a Cost-Effective Mechanochemical Method for Photovoltaic Applications

“…A tetragonal distortion value, that is, the c /2 a ratio of 1, was observed in all the prepared CZTS samples. These results confirm that the kesterite structure is consistent with those from previously published reports [ 22 , 32 ]. The average crystallite size was calculated to be 6–109 nm using the Debye–Scherrer equation, whereas the average crystallite size obtained from Williamson–Hall measurements was between 5 and 61 nm.…”

“…However, the power conversion efficiency is far lower than the reported conversion efficiency of a CZTS-based photovoltaic device (9.2% to 11.0%) using an absorber fabricated by a vacuum-based technique (evaporation, co-sputtering, and RF-magnetron sputtering) [ 65 , 66 ]. This could be because all the CZTS samples contain small-sized grains [ 49 , 67 , 68 ], possibly because of the non-optimized process of sulfurization [ 49 , 67 , 68 ] and Na incorporation [ 22 , 23 ]. Zn-rich and Cu-poor compositions (Zn/Sn = 1.2 and Cu/(Zn + Sn) = 0.8) are ideal conditions for high conversion efficiency; thus, the elemental composition of CZTS samples requires optimization [ 49 , 69 , 70 ].…”

“…In addition to the selection of low-cost syntheses, alkali-metal-incorporation strategies have been used to increase the performance of photovoltaic cells. The use of alkali metals, particularly Na, has been observed to have positive effects on kesterite-based absorber layers and photovoltaic devices [ 21 , 22 , 23 ]. Experimental and theoretical studies have demonstrated that one of the limitations of the photoconversion efficiency of CZTS thin film-based devices is the existence of inherent defects at the interface and grain boundary, which can be effectively passivated by the incorporated Na.…”

“…Experimental and theoretical studies have demonstrated that one of the limitations of the photoconversion efficiency of CZTS thin film-based devices is the existence of inherent defects at the interface and grain boundary, which can be effectively passivated by the incorporated Na. As a result, grain growth and (112) texturization improvement, scattering, and recombination centers can be reduced in the absorber layer, suppressing non-radiative recombination, reducing charge traps, and improving the electrical properties of the absorber layer [ 22 , 24 , 25 , 26 , 27 ]. Oo et al reported grain growth in CZTS films prepared on soda-lime glass (SLG) or immersed in an aqueous solution of Na 2 S [ 28 ].…”

“…Sun et al achieved a CZTS device efficiency of 6.2% using Na-doped Mo as the back-contact electrode on a flexible stainless-steel substrate [ 30 ]. Recently, Hao et al reported an improved CZTS device efficiency from 2.37% to 3.26% [ 22 ]. Jiang et al reported 2.3% CZTS device efficiency using a bifacial Na layer strategy [ 23 ].…”