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

Abstract Antimony sulfide (Sb 2 S 3 ) has attracted extensive attention due to its excellent photoelectric characteristics, including a high absorption coefficient (α > 10 4 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 Sb 2 S 3 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 Sb 2 S 3 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 Sb 2 S 3 ‐based solar device (FTO/CdS/Sb 2 S 3 /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 Sb 2 S 3 thin films by CBD method as well as a potential route for enhancing Sb 2 S 3 solar cell performance.