Abstract
Grain boundaries in Cu2ZnSn(SxSe1x)4 (CZTSSe) thin films act as a defect that reduces the mobility of the
charges. Hence one way to improve the performance of these thin film solar cells is to increase the grain
size in the films. Most of the synthesis methods published so far for CZTSSe colloidal nanoparticles can
achieve a general size distribution range from 5–20 nm. This is where the particle size will saturate for
most recipes used today. The assumption is that uniform size distribution is good for grain growth in
a thin film but based on packing considerations, an optimal mixture of large and small nanoparticles that
can easily be dispersed in non-polar solvents could be better. Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4
(CZTSe) nanoparticles are synthesized using the hot-injection method with oleylamine,
trioctylphosphine, and hexadecane as the solvents. Selenium (Se) is introduced in the liquid phase to
encourage grain growth – liquid selenization. This eliminates the need to anneal the film in a Secontaining
atmosphere and allows for a more environmentally friendly process with lower temperatures
and shorter annealing times. We show that a good dispersion can be achieved by choosing suitable
surfactant molecules, solvents and precursors, and by controlling the initial monomer concentration.
Additionally, we show how our new synthesis route can be utilized to achieve targeted ratios of CZTS
and CZTSe nanoparticles to be used for mixed-phase CZTSSe thin films.
Original language | English |
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Journal | RSC Advances |
Volume | 5 |
Pages (from-to) | 96593-96600 |
ISSN | 2046-2069 |
DOIs | |
Publication status | Published - 2015 |