Interlayer-mediated oriented growth and defect passivation toward efficient bulk heterojunction Sb₂(S,Se)₃...

Antimony selenosulfide (Sb₂(S,Se)₃) has garnered considerable interest as a high-absorption photovoltaic material due to its exceptional light-harvesting properties. However, bulk heterojunction (BHJ) Sb₂(S,Se)₃ solar cells-though promising for efficient charge dissociation-still suffer from inefficient carrier extraction and high non-radiative losses, primarily caused by disordered crystallization and defective interfaces. Herein, we propose an interlayer-mediated oriented growth and defect passivation (IOD) strategy, utilizing a CdS seed layer (SL-CdS), to fabricate high-quality Sb₂(S,Se)₃ BHJ films with controlled morphology and optoelectronic properties. The SL-CdS interlayer guides the crystallization process, inducing preferential growth along the [h k l, l ≠ 0] crystallographic direction while suppressing [hk0]-oriented domains, thereby facilitating anisotropic charge transport along the c-axis and reducing carrier scattering. Moreover, this approach significantly reduces defect density by 47.37 % and diminishes non-radiative recombination by 74.64 %, while also enhancing charge carrier mobility and strengthening the built-in electric field. As a result, the champion BHJ Sb₂(S,Se)₃ solar cell achieves a remarkable power conversion efficiency (PCE) of 8.46 %-one of the highest reported for such BHJ architectures-representing a nearly threefold improvement over control device. Through multiscale characterization and detailed performance analysis, we conclusively correlate the enhanced photovoltaic performance with tailored grain orientation and size, effective interface passivation, and optimized carrier dynamics. This work provides a new materials design paradigm via interlayer engineering for high-performance and low-loss chalcogenide photovoltaics.