title: Solvent-free synthesis of Cu2ZnSnS4 nanocrystals: a facile, green, up-scalable route for low cost photovoltaic cells.
abstract: Efficient Cu2ZnSnSe4 (CZTSe) solar cells were fabricated with a simple, environmentally friendly, and scalable synthetic method for Cu2ZnSnS4 (CZTS) nanocrystals. CZTS nanoparticles were mechanochemically synthesized from elemental precursors on a relatively large scale (∼20 g), during which no solvents or additives were used, thus alleviating the complex process of particle synthesis. An analysis of the time evolution of the crystalline phase and morphology of precursor powders revealed that the formation of the CZTS compound was completed in 0.5 h once initiated, suggesting that the mechanochemically induced self-propagating reaction prevails. CZTS ink was prepared by dispersing the as-synthesized nanoparticles in an environmentally benign solvent (160 mg mL(-1) in ethanol) without using any additives, after which it was cast onto Mo-coated glass substrates by a doctor-blade method. Subsequent reactive annealing at 560 °C under a Se-containing atmosphere resulted in substantial grain growth along with the nearly complete substitution of Se. The CZTSe solar cells therefrom exhibited power conversion efficiency levels as high as 6.1% (based on the active area, 0.44 cm(2)) with a relatively high open-circuit voltage (0.42 V) in comparison with the bandgap energy of 1.0 eV.
authors.affiliation: Center for Materials Architecturing, Korea Institute of Science and Technology (KIST), Seoul 136-791, Korea. sohyec@kist.re.kr.
authors.forename: Bo-In
authors.initials: BI
authors.lastname: Park
authors.forename: Yoonjung
authors.initials: Y
authors.lastname: Hwang
authors.forename: Seung Yong
authors.initials: SY
authors.lastname: Lee
authors.forename: Jae-Seung
authors.initials: JS
authors.lastname: Lee
authors.forename: Jong-Ku
authors.initials: JK
authors.lastname: Park
authors.forename: Jeunghyun
authors.initials: J
authors.lastname: Jeong
authors.forename: Jin Young
authors.initials: JY
authors.lastname: Kim
authors.forename: BongSoo
authors.initials: B
authors.lastname: Kim
authors.forename: So-Hye
authors.initials: SH
authors.lastname: Cho
authors.forename: Doh-Kwon
authors.initials: DK
authors.lastname: Lee