The
environmentally friendly antimony selenosulfide (Sb2(S,Se)3) semiconductor emerges as a promising light harvester
for thin-film photovoltaics owing to its excellent material and optoelectronic
properties. The alloyed Sb2(S,Se)3 is endowed
with the complementary benefits of Sb2S3 and
Sb2Se3, such as a tunable band gap within the
range of 1.10–1.70 eV. In Sb2(S,Se)3 solar
cells, the n-type semiconductor CdS is extensively used as an electron
transport layer (ETL), which plays a role in extracting photogenerated
electrons from absorbers and transporting them to conducting substrates.
However, the unsatisfactory ETL/absorber interface contact often involves
severe interface recombination. Herein, we report that an ultrathin
SnO2 buffer layer of ∼10 nm applied on the high-roughness
fluorine-doped tin oxide (FTO) substrate aids in effective interface
and band engineering for superstrate CdS/Sb2(S,Se)3 solar cells. Careful characterizations confirm that the ultrathin
SnO2 buffer layer plays a positive role in inhibiting the
shunt current leakage at the ETL/absorber interface and manipulating
the cascade energy band structure for more effective interface passivation
and efficient electron extraction. Consequently, the resultant SnO2/CdS ETL-based Sb2(S,Se)3 solar cells
exhibited a remarkable device efficiency of 8.67%, coupled with a
considerable open-circuit voltage of 0.72 V. Our finding demonstrates
a facile approach to engineer the interface contact and band offset
to accelerate electron extraction, transport, and collection efficiencies.
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