1D/3D Alloying Induced Phase Transition in Light Absorbers for Highly Efficient Sb<sub>2</sub>Se<sub>3</sub> Solar Cells
Chunsheng Guo, Xiaoyang Liang, Tao Liu, Yufan Liu, Lin Yang, Weidong Lai, R.E.I. Schropp, Dengyuan Song, Yaohua Mai, Zhiqiang Li
Abstract
A simple binary inorganic antimony selenide (Sb 2 Se 3 ) compound is attractive as a promising light absorber for low‐cost and high‐efficiency photovoltaics. The external quantum efficiencies of Sb 2 Se 3 solar cells are now approaching the optical limit values, which are comparable with the traditional well‐developed solar cells (such as Si, CuInGaSe 2 , CdTe, etc). However, the power conversion efficiency of the Sb 2 Se 3 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 AgSbSe 2 phase, formed by phase transition from low symmetry binary Sb 2 Se 3 , is introduced to control the doping density in the alloyed (Sb 2 Se 3 ) x (AgSbSe 2 ) 1− x films utilizing configurational entropy. Guided by this alloying concept, 1D–3D (Sb 2 Se 3 ) x (AgSbSe 2 ) 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 (Sb 2 Se 3 ) x (AgSbSe 2 ) 1− x alloy absorber layer, compared with the reference cell with a pure Sb 2 Se 3 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 Sb 2 Se 3 ‐based solar cells.