Self‐Regulated Growth of Large‐Grain Sb₂S₃ Thin Films for High‐Efficiency Solar Cells

Abstract Antimony sulfide (Sb₂S₃) has attracted extensive attention due to its excellent photoelectric characteristics, including a high absorption coefficient (α > 10⁴ cm⁻¹) and a suitable bandgap (≈1.7 eV). However, due to its Q1D (quasi‐1D) structure, numerous deep‐level defects are identified in the Sb₂S₃ film, limiting the device's performance, and necessitating more efforts to overcome this situation. In this context, an ethanol solvent‐assisted chemical bath deposition (S‐CBD) strategy, a novel high‐quality thin film manufacturing technique is presented that modifies the supersaturation of the precursor solution by varying the boiling point and solvent polarity. This approach enables the effective regulation of the correlation between the crystal nucleation and growth rates, resulting in Sb₂S₃ films with large grains (≈4.25 µm, 37.5% ethanol), excellent crystallinity, well‐oriented structures (TC₍₂₁₁₎/TC₍₀₂₀₎ = 2.39), low defect density, and prolonged carrier lifetimes (τ_Ave ≈ 12.1 ns). Consequently, the final Sb₂S₃‐based solar device (FTO/CdS/Sb₂S₃/Spiro‐OMeTAD/Au) shows significant improvements in both FF (61.63%) and J_SC (17.61 mA cm⁻²), yielding an excellent power conversion efficiency (PCE) of 7.84%. This research gives particular insights into the growth mechanism of high‐quality Sb₂S₃ thin films by CBD method as well as a potential route for enhancing Sb₂S₃ solar cell performance.