Ternary Cu
2
SnS
3
(CTS) is an attractive nontoxic
and earth-abundant absorber material with suitable optoelectronic
properties for cost-effective photoelectrochemical applications. Herein,
we report the synthesis of high-quality CTS nanoparticles (NPs) using
a low-cost facile hot injection route, which is a very simple and
nontoxic synthesis method. The structural, morphological, optoelectronic,
and photoelectrochemical (PEC) properties and heterojunction band
alignment of the as-synthesized CTS NPs have been systematically characterized
using various state-of-the-art experimental techniques and atomistic
first-principles density functional theory (DFT) calculations. The
phase-pure CTS NPs confirmed by X-ray diffraction (XRD) and Raman
spectroscopy analyses have an optical band gap of 1.1 eV and exhibit
a random distribution of uniform spherical particles with size of
approximately 15–25 nm as determined from high-resolution transmission
electron microscopy (HR-TEM) images. The CTS photocathode exhibits
excellent photoelectrochemical properties with PCE of 0.55% (fill
factor (FF) = 0.26 and open circuit voltage (Voc) = 0.54 V) and photocurrent
density of −3.95 mA/cm
2
under AM 1.5 illumination
(100 mW/cm
2
). Additionally, the PEC activities of CdS and
ZnS NPs are investigated as possible photoanodes to create a heterojunction
with CTS to enhance the PEC activity. CdS is demonstrated to exhibit
a higher current density than ZnS, indicating that it is a better
photoanode material to form a heterojunction with CTS. Consistently,
we predict a staggered type-II band alignment at the CTS/CdS interface
with a small conduction band offset (CBO) of 0.08 eV compared to a
straddling type-I band alignment at the CTS/ZnS interface with a CBO
of 0.29 eV. The observed small CBO at the type-II band aligned CTS/CdS
interface points to efficient charge carrier separation and transport
across the interface, which are necessary to achieve enhanced PEC
activity. The facile CTS synthesis, PEC measurements, and heterojunction
band alignment results provide a promising approach for fabricating
next-generation Cu-based light-absorbing materials for efficient photoelectrochemical
applications.
Cadmium sulfide (CdS) nanoparticles were synthesized by simple and low cost homemade hot injection method at low process temperature using different sulphur sources. The effects of sulphur concentration on the structural, morphological, and optoelectronic properties of synthesized CdS films were studied using a range of characterization techniques: X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) and UV-Visible spectroscopy. The XRD studies revealed the formation of hexagonal type CdS nanoparticles. The varying morphology dependence on the sulphur source was ascertained from FESEM analysis. The longitudinal optical (LO) phonon vibrational modes of CdS were assigned in Raman spectra at 300 and 600 cm-1. The band gap of the CdS particles was estimated to be 2.30 eV from Tauc's plots. Consistent with the experimental results, our first-principles DFT calculations predict the band gap of CdS nanoparticles to increase with decreasing S concentration: Cd 52 S 52 (2.38 eV) Cd 52 S 51 (2.52 eV) and Cd 52 S 50 (2.65 eV), with both the valence and conduction band edges demonstrated to be dominated by S-p states.
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