Back Interface and Absorber Bulk Deep‐Level Trap Optimization Enables Highly Efficient Flexible Antimony Triselenide Solar Cell

Abstract The unique 1D crystal structure of Antimony Triselenide (Sb 2 Se 3 ) offers notable potential for use in flexible, lightweight devices due to its excellent bending characteristics. However, fabricating high‐efficiency flexible Sb 2 Se 3 solar cells is challenging, primarily due to the suboptimal contact interface between the embedded Sb 2 Se 3 layer and the molybdenum back‐contact, compounded by complex intrinsic defects. This study introduces a novel Molybdenum Trioxide (MoO 3 ) interlayer to address the back contact interface issues in flexible Sb 2 Se 3 devices. Further investigations indicate that incorporating a MoO 3 interlayer not only enhances the crystalline quality but also promotes a favorable [hk1] growth orientation in the Sb 2 Se 3 absorber layer. It also reduces the barrier height at the back contact interface and effectively passivates harmful defects. As a result, the flexible Sb 2 Se 3 solar cell, featuring a Mo‐foil/Mo/MoO 3 /Sb 2 Se 3 /CdS/ITO/Ag substrate structure, demonstrates exceptional flexibility and durability, enduring large bending radii and multiple bending cycles while achieving an impressive efficiency of 8.23%. This research offers a straightforward approach to enhancing the performance of flexible Sb 2 Se 3 devices, thereby expanding their application scope in the field of photovoltaics.