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Page 4 of 13 Xia et al. Energy Mater. 2026, 6, 600022

solution. Immerse the Sb2S3 film in the above solution in a 100 mL Teflon-lined autoclave, seal it, and heat it
at 120 °C for 35 min. Apply carbon ink on the HTL and bake it at 120 °C on a hot plate for 30 min. Apply
silver paste on the carbon layer and bake it at 80 °C for 10 min to complete the device fabrication. The total
fabrication time for a complete device is approximately 2 to 3 days. Finally, a total of 54 devices were
fabricated to validate the statistical reliability of the results.

Characterization
In this work, we used a field emission scanning electron microscope (SU-8010; Hitachi High-Tech, Japan)
equipped with energy dispersive X-ray (EDX) to characterize the surface and elemental composition of the
selenated antimony original mineral films. The crystal structures of the surface and powder of the selenated
antimony original mineral films were characterized by X-ray diffraction (Ultima IV; Rigaku Corporation,
Japan). The transmittance of the thin film was measured by ultraviolet–visible spectroscopy (UV-Vis)
absorption spectroscopy (Lambda 950; PerkinElmer, USA). The current density-voltage (J-V) curves were
collected using a Keithley 2400 source meter (Keithley 2400; Keithley Instruments, USA) under simulated
AM 1.5G by the solar simulator (Newport 94023A; Newport Corporation, USA). The external quantum
efficiency (EQE) of the devices was performed by a solar cell quantum efficiency measurement system
(QEX10; PV Measurements, Inc., USA). Carrier transport and recombination mechanisms were investigated
through electrochemical impedance spectroscopy (EIS) and dark capacitance-voltage (C-V) analysis. The
Raman measurement was performed using the LABRAM-HR microRaman system with a 532 nm laser light
source (LabRAM HR Evolution; HORIBA Scientific, France).

RESULTS AND DISCUSSION
The surface morphology of Sb S precursor films, with and without the ZnO modification layer, was first
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analyzed by scanning electron microscopy (SEM). As depicted in Supplementary Figure 1, the deposition of
an ultrathin ZnO layer did not significantly alter the initial morphology; both samples displayed
characteristic large-grained structures formed from agglomerated nanocrystals, typical of hydrothermally
grown Sb S films. However, post-annealing morphological evolution revealed stark contrasts, as shown in
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Figure 1. The unmodified sample (W/O ZnO) formed ~50 nm Sb O /Sb S particles and ~40 nm Sb O 3
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nanobelts at grain boundaries. By contrast, ZnO-coated films exhibited notable morphological refinements:
the 20 s ZnO sample showed smaller particles (~30 nm) and narrower nanobelts (~20 nm), with coarsening
observed at longer deposition times. This coarsening is attributed to ZnO-mediated suppression of Sb S
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volatilization, which increases the local Sb S availability for oxidation and promotes Sb O growth supported
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by subsequent compositional analysis.
Cross-sectional SEM imaging (the inset of Figure 1) corroborated these findings. The control film (W/O
ZnO) displayed a highly uneven thickness (~350 nm) due to extensive Sb S loss during annealing, along with
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the presence of large Sb O surface particles. Incorporation of a 20 s ZnO layer mitigated volatilization,
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resulting in a more uniform film with increased thickness (~500 nm). Extended ZnO deposition (≥ 40 s)
further improved thickness (up to ~600 nm) and significantly reduced Sb O surface features. Elemental
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analysis via energy-dispersive X-ray spectroscopy (EDS) quantified atomic percentages of Sb, S, O, and Zn
[Supplementary Figure 2A]. Key trends include: (1) relatively stable Sb content, (2) a non-monotonic
variation in S content, (3) an initial decrease followed by an increase in O content, and (4) a clear upward
trend in Zn concentration (from ~0.1% to ~1.2 at.%). The elevated oxygen and decreased sulfur levels at
400 s ZnO are attributed to thick ZnO layers contributing additional oxygen. The increasing Zn/Sb atomic
ratio [Supplementary Figure 2B] further confirms progressive Zn incorporation into the Sb S matrix with
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extended ZnO exposure.