1D/3D Alloying Induced Phase Transition in Light Absorbers for Highly Efficient Sb₂Se₃ Solar Cells

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 (V_OC) 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 V_OC 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.