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Antimony selenide (Sb2Se3) nanorod arrays along the [001] orientation are known to transfer photogenerated carriers rapidly due to the strongly anisotropic one‐dimensional crystal structure. With advanced light‐trapping structures, the Sb2Se3 nanorod array‐based solar cells have excellent broad spectral response properties, and higher short‐circuit current density than the conventional planar structured thin film solar cells. However, the interface engineering for the Sb2Se3 nanorod array‐based solar cell is more crucial to increase the performance, because it is challenging to coat a compact buffer layer with perfect coverage to form a uniform heterojunction interface due to its large surface area and length–diameter ratio. In this work, an intermeshing In2S3 nanosheet‐CdS composite as the buffer layer, compactly coating on the Sb2Se3 nanorod surface is constructed. The application of In2S3‐CdS composite buffers build a gradient conduction band energy configuration in the Sb2Se3/buffer heterojunction interface, which reduces the interface recombination and enhances the transfer and collection of photogenerated electrons. The energy‐level regulation minimizes the open‐circuit voltage deficit at the interfaces of buffer/Sb2Se3 and buffer/ZnO layers in the Sb2Se3 solar cells. Consequently, the Sb2Se3 nanorod array solar cell based on In2S3‐CdS composite buffers achieves an efficiency of as high as 9.19% with a VOC of 461 mV. [ABSTRACT FROM AUTHOR]

A simple binary inorganic antimony selenide (Sb2Se3) compound is attractive as a promising light absorber for low‐cost and high‐efficiency photovoltaics. The external quantum efficiencies of Sb2Se3 solar cells are now approaching the optical limit values, which are comparable with the traditional well‐developed solar cells (such as Si, CuInGaSe2, CdTe, etc). However, the power conversion efficiency of the Sb2Se3 devices is constrained by the open‐circuit voltage (VOC) deficit, due to the intrinsic high resistivity and low element‐doping efficiency in such one‐dimensional (1D) crystals. Herein, a highly conductive, three‐dimensional (3D) crystal‐structure AgSbSe2 phase, formed by phase transition from low symmetry binary Sb2Se3, is introduced to control the doping density in the alloyed (Sb2Se3)x(AgSbSe2)1−x films utilizing configurational entropy. Guided by this alloying concept, 1D–3D (Sb2Se3)x(AgSbSe2)1−x alloy films with tunable doping densities are obtained. As a consequence, a noticeable improvement in VOC by >18% is observed in solar cells based on the (Sb2Se3)x(AgSbSe2)1−x alloy absorber layer, compared with the reference cell with a pure Sb2Se3 absorber, leading to a high conversion efficiency of 7.8%. This alloying model provides a universal approach to control the photoelectrical properties for high‐efficiency Sb2Se3‐based solar cells. [ABSTRACT FROM AUTHOR]