Grain Size and Absorber Thickness Than Solely Controlling Orientation for Fabricating High-Performance Sb₂Se₃ Solar Cells

Although substantial research efforts have been devoted to controlling and modulating the grain orientations of Sb₂Se₃ thin films to improve efficiency, a theoretical investigation into how grain orientation affects photovoltaic performance remains lacking. This lag in theoretical investigations hinders practical design and fabrication for high-performance Sb₂Se₃ thin-film solar cells. Herein, finite-element simulations have been performed, especially first taking unique anisotropic charge-transport properties into account, to reveal the fundamental relationship between grain orientation and device performance, demonstrating a 125% increase in power conversion efficiency (PCE) when the preferred orientation changes from [010] to [001]. Critically, we demonstrate that sufficiently large grain sizes (>1.5 μm) or thin absorber thicknesses (<0.4 μm) can effectively suppress the negative effect of nonpreferred grain orientations, particularly in multiorientation systems. Thus, the PCE demonstrates a maximum value of 18.52% for Sb₂Se₃ thin-film solar cells with 2-μm grains when the thickness = 0.6 μm, accomplished with a <i>V</i>_OC of 0.75 V, <i>J</i>_SC of 31.64 mA/cm², and FF of 76.35%. These results establish a quantitative understanding of the effect of grain orientations on device performance and propose a practical strategy for fabricating high-efficiency Sb₂Se₃ thin-film solar cells in a low-cost, controllable process.