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.
Antimony chalcogenide semiconductors have received much attention for serving as promising light harvesters owing to their excellent materials and photoelectric properties. Particularly, Sb2(S,Se)3 alloyed materials share the complementary advantages of Sb2S3 and Sb2Se3, showing a tunable bandgap ranging from 1.1 to 1.7 eV. In Sb2(S,Se)3 solar cells, although Sb2(S,Se)3 absorber material shows a friendly character to the environment, the widely used CdS electron transport layer (ETL) that often affords considerable device efficiencies is not environmental friendly; moreover, CdS often suffers from severe parasitic light absorption due to its relatively narrow band gap of 2.4 eV. Hence, the exploration of Cd‐free or less‐Cd‐based ETLs is urgently needed. Herein, SnO2‐dominated ETLs are carefully designed by optimizing the concentration of SnO2 precursor solutions and spin‐coating cycles, and are further constructed over 8%‐efficient Sb2(S,Se)3 solar cells, together with the effective modification of SnO2/Sb2(S,Se)3 with an ultrathin CdS layer. The morphological and optical–electrical properties of ETLs, the performance of solar cells, and the related charge recombination mechanisms are discussed. The designed SnO2‐dominated ETLs have sharply decreased the use of heavy metal Cd, thereby reducing the risk of environmental pollution. This work provides important enlightenment for designing totally environmentally friendly Sb2(S,Se)3 solar cells.
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