Extremely thin absorber (ETA) solar cells integrating ZnO nanowires have been receiving increasing interest owing to efficient light-trapping phenomena and charge-carrier management, but the chemical instability of ZnO in acidic conditions limits its combination with a variety of absorbing semiconducting shells grown by chemical deposition techniques. By covering the ZnO nanowires grown by chemical bath deposition with a protective, passivating, conformal, thin, anatase-TiO2 layer by atomic layer deposition, we show that a uniform Sb2S3 absorbing shell is formed by chemical spray pyrolysis without structural degradation of the ZnO. The Sb2S3 absorbing shell consists of a very thin, conformal layer together with homogeneously distributed small clusters from the bottom to the top of the ZnO/TiO2 core–shell nanowire arrays. The resulting ETA solar cells integrating these ZnO/TiO2/Sb2S3 core–shell nanowire heterostructures with an Sb2S3 absorbing shell less than 10 nm-thick and P3HT as the hole-transporting material have a photoconversion efficiency of 2.3% with a promising short-circuit current density of 7.5 mA/cm2 and a high open-circuit voltage of 656 mV as one of the largest reported values in ZnO nanowire-based ETA solar cells. The present findings thus reveal the great potential of Sb2S3 as an absorbing, semiconducting shell when coupled with ZnO/TiO2 core–shell nanowire heterostructures, opening the way for new strategies to improve the performance of ZnO nanowire-based ETA solar cells fabricated by low-cost, surface-scalable, easily implemented chemical deposition techniques.

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The ZnS layers morphology, structure, composition, and optical properties were investigated with respect to the precursors (zinc chloride and thiocarbamide, Zn:S) molar ratio in spray solution (1:1, 1:2, and 1:3) and growth temperatures in the range of 400–600 °C. Scanning electron microscopy (SEM), X‐ray diffraction (XRD), energy dispersive X‐ray analysis (EDX), UV–VIS, and PL spectroscopy were applied to characterize the ZnS layers. Layers obtained at temperatures up to 450 °C are not well crystallized and contain residues originated from undecomposed precursors. ZnS films become crystalline at Ts = 500 °C. Layers grown from 1:1 solution at 550 °C are mixture of ZnS and ZnO phases, whereas at 600 °C layers of ZnO were obtained. Films produced from 1:2 solution at 500–600 °C are of ZnS with a wurtzite structure and Eg of 3.66 eV, but contain traces of ZnO phase when grown at 550 or 600 °C. Appearance of ZnO phase in the films grown from 1:1 and 1:2 solutions is explained by the results of the studies on the formation and decomposition of dichlorobis(thiocarbamide)zinc(II) complex as an intermediate compound formed in the solution of zinc chloride and thiocarbamide. Spraying the solutions with Zn:S = 1:3, which contain more thiocarbamide than required for the complex formation, results in single‐phase ZnS layers with wurtzite structure at growth temperatures up to 600 °C. Moreover, ZnS layers obtained from 1:3 solution at 550 °C and higher are composed of highly c‐axis oriented ZnS nanorod‐like crystals with diameter of ca. 80 nm and length of ca. 300 nm.