A gas-templating strategy to synthesize CZTS nanocrystals for environment-friendly solar inks

Abstract

This is an author's version published in: http://oatao.univ-toulouse.fr/23530 a b s t r a c t A high-temperature gas-templating strategy is proposed to synthesize Cu 2 ZnSnS 4 (CZTS) nanocrystals for all-aqueous solar inks. Our gas templating process route involves the in-situ generation and stabilization of nanosized gas bubbles into a molten KSCN-based reaction mixture at 400°C. Chemical insights of the templating gas process are provided such as the simultaneous formation of gas bubbles and CZTS nuclei highlighting the crucial role of the nucleation stage on the sponge and resulting nanocrystals properties. The high porosity displayed by the resulting CZTS nanocrystals facilitates their further post-fragmentation, yielding individualized nanocrystals. The advantages of our high temperature gas templating route are illustrated by the following: (i) the low defect concentration displayed by the highly crystalline nanocrystals, (ii) the synthesis of CZTS nanocrystals displaying S 2 À polar surfaces after ligand exchange. The good photoluminescence properties recorded on the pure CZTS nanocrystals reveal potential for exploration of new complex chalcogenide nanocrystals useful for various applications including photovoltaics and water splitting. Here we demonstrate that using these building blocks, a CZTS solar cell can be successfully fabricated from an environment-friendly all-aqueous ink.n Corresponding author. Tel.: þ 33 5 6155 6115; fax: þ 33 5 6155 6163.

Water-soluble, heterometallic chalcogenide oligomers as building blocks for functional films

“…S 2− , 47 (Sn 2 S 6 ) 4− molecular metal chalcogenides 17 were recently proposed to replace organic capping ligands on chalcogenide nanocrystals. The ability of a (Sn a -Zn b -S c ) t− oligomer solution (x Zn = 0.33) to efficiently strip off SCN − surface groups from our CZTS nanoparticles synthesized at a high temperature of 400 °C in molten KSCN 27 was demonstrated by infrared spectroscopy (Fig. 10).…”

“…Details of their synthesis and nanocrystal properties are reported in ref. 27. Carbon-containing surface species such as SCN − identified on the as-synthesized nanocrystals 27 were solution-exchanged using a (Sn a -Zn b -S c ) t− oligomer solution initially prepared at x Zn = 0.33.…”

“…27. Carbon-containing surface species such as SCN − identified on the as-synthesized nanocrystals 27 were solution-exchanged using a (Sn a -Zn b -S c ) t− oligomer solution initially prepared at x Zn = 0.33. In a typical experiment, CZTS nanocrystals prepared as described in ref.…”

“…In a typical experiment, CZTS nanocrystals prepared as described in ref. 27 were ball-milled in EtOH and later extensively washed with H 2 O. After successive centrifugation and redispersion in H 2 O, colloidal aqueous dispersions of CZTS nanocrystals were collected and made to come into contact with a (Sn a -Zn b -S c ) t− , x Zn = 0.33, oligomer solution prepared at 0.1 M ([Sn] + [Zn]).…”

“…To produce all-aqueous inks, tin chalcogenide complexes including Sn 2 S 6 4− and Sn 2 S 7 6− were proposed as ligands to in situ cap the Cu/Zn sulfide nanoparticles, 26 resulting in homogeneous and stable dispersions for the formation of CZTS,Se films. Another environmentally friendly approach was developed in our group involving a high temperature nanocrystal synthetic route 27 producing low electronic-defect concentration Cu 2 ZnSnS 4 (CZTS) building blocks. The surfaces of these CZTS nanocrystals were further purified by S 2− exchange, yielding deagglomerated Cu 2 ZnSnS 4 nanocrystal dispersions.…”