Thermally Activated Chain Reconfiguration Enabled by Selenium Incorporation for Efficient Carrier Transport in Antimony Sulfide Thin-Film Solar Cells

Abstract

Antimony sulfide (Sb2S3) has emerged as a highly promising inorganic thin-film light-absorbing material owing to its suitable bandgap, high absorption coefficient, and excellent thermal stability. However, the deep-level defects and intrinsic carrier self-trapping effects arising from its quasi-one-dimensional crystal structure severely limit device efficiency. In this work, selenium (Se) was introduced via magnetron sputtering, followed by a thermally activated molecular-chain reconfiguration process to enhance lattice stability and carrier transport. During this process, Se atoms diffuse into the Sb2S3 lattice and migrate toward grain boundaries, forming a vertical compositional gradient that modulates film crystallinity, growth orientation, and band structure. Due to its larger atomic radius, Se incorporation induces slight lattice expansion and strain redistribution, effectively passivating sulfur vacancies and suppressing SSb antisite defects. Phonon-spectrum simulations and differential charge-density analyses confirm that Se incorporation mitigates lattice distortion, suppresses carrier self-trapping, and enhances carrier delocalization. The optimized Se-Sb2S3 films exhibit improved crystallinity, prolonged carrier lifetime, and reduced nonradiative recombination losses, achieving a power conversion efficiency of 7.82%. This study reveals a thermodynamically driven defect-passivation mechanism and provides a viable strategy for developing efficient and stable Sb2S3-based solar cells.