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Xia et al. Energy Mater. 2026, 6, 600022 Page 3 of 13

passivation of the underlying Sb S film via a lattice-vacancy-mediated mass transfer mechanism, effectively
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inhibiting the formation of Sb O and reducing interface defects, etc. Critically, the selection of ZnO also
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considers potential Zn substitutional doping at the Sb S /oxide interface, which modulates interfacial energy
2+
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levels and enhances carrier concentration. This synergistic approach concurrently optimizes the phase
composition, morphology, and electrical properties of the Sb S back surface, thereby improving
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carrier transport efficiency. Ultimately, a PCE of 7.00% was achieved in a fully inorganic fluorine-doped tin
oxide (FTO)/CdS/Sb S /PbS/Carbon/Ag architecture, offering a novel route toward more efficient and stable
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Sb S solar cells.
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EXPERIMENTAL
Chemicals
Cadmium nitrate tetrahydrate [Cd(NO ) ·4H O], ammonium hydroxide (NH ·H O), thiourea (CH N S), and
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cadmium chloride hemipentahydrate (CdCl ·2.5H O) were purchased from Sinopharm Chemical Reagent
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Co., Ltd. (Shanghai, China). Methanol (CH OH), potassium antimony tartrate hemihydrate
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(C H KO Sb·0.5H O), and lead acetate trihydrate (PbC H O ·3H O) were supplied by Shanghai Macklin
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Biochemical Co., Ltd. (Shanghai, China). Zinc oxide (ZnO), and sodium thiosulfate pentahydrate
(Na S O ·5H O) were supplied by Aladdin Reagent Co., Ltd. (Shanghai, China). The carbon ink (C, CH-8)
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was supplied by Jujo printing supplies & Technology Co. Ltd. (Zhejiang, China). The silver conductive paint
(Ag, 05002-AB) was supplied by Structure Probe, Inc (USA). All the chemicals were used as received without
further purification.
CdS electron transport layer preparation
Commercial FTO was ultrasonically cleaned with detergent, acetone, anhydrous ethanol, and ultrapure water
sequentially for 60 min, dried, and ozone-treated for 20 min to remove surface organics/impurities. The FTO
substrate with the conductive surface facing down was placed into a 100 mL deionized water solution
containing 0.15 mM cadmium nitrate tetrahydrate, 9.4 mM thiourea and 0.19 mol ammonium hydroxide.
The mixed solution was then placed in a 65 °C water bath for 15 min to deposit the CdS film. To improve the
crystallinity, 0.05 g CdCl ·2.5H O dissolved in 10 mL methanol was spin-coated on CdS, annealed in air at
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380 °C for 5 min, then cooled naturally.
Sb 2 S 3 and ZnO preparation
Dissolve 0.12 mol of sodium thiosulfate pentahydrate as the sulfur source and 0.06 mol of potassium
antimony tartrate hemihydrate as the antimony source in 40 mL of deionized water respectively, then mix
them to form 80 mL of solution. The mixture and three FTO/CdS substrates were transferred into a 100 mL
Teflon-lined autoclave vessel. Seal the autoclave and heat it at 120 °C for 12 h. After the hydrothermal
reaction, wash the sample with deionized water and then dry it under normal pressure on a hot plate to
obtain the Sb S precursor film.
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Prepare the ZnO protective layer by radio frequency magnetron sputtering. The specific process parameters
are as follows: the sputtering base pressure is less than 1.0 × 10 Pa, the working gas is a mixture of argon and
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oxygen (Ar:O = 9:1), the sputtering power is set at 60 W, and the sputtering time is controlled at 20-400 s.
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Then, place the sample in a closed space and perform annealing in an ambient air atmosphere in an inverted
manner. The annealing temperature is 450 °C for 3 min. Nine devices were fabricated under each
experimental condition to support statistical analysis.

HTL and Electrode fabrication
Deposit PbS by in-situ hydrothermal method. Dissolve 3.3 mM of lead acetate trihydrate (PbC H O ·3H O)
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and 17.4 mM of sodium thiosulfate pentahydrate (Na S O ·5H O) in 50 mL of deionized water to form a clear
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