Mechanism of Defect Passivation in Sb2Se3 Solar Cells via Buried Selenium Seed Layer

A novel approach is developed by incorporating buried selenium seed layers to enhance the performance of Sb₂Se₃ solar cells through improved heterojunction quality and reduced defect density. This method significantly boosts both V _OC and PCE, reaching 498.3 mV and 8.42%, respectively, marking the highest efficiency reported for Sb₂Se₃ solar cells prepared via VTD.

Abstract

Quasi-1D antimony selenide (Sb₂Se₃) is known for its stable phase structure and excellent light absorption coefficient, making it a promising material for high-efficiency light harvesting. However, the (Sb₄Se₆)_n ribbons align horizontally, increasing defect interference and limiting vertical carrier transport. Herein, a novel strategy of burying selenium (Se) seed layers to reduce lattice mismatch at the heterojunction interface, promote crystal orientation, mitigate deep donor defects, increase P-type carrier concentration, and purify the PN junction, is proposed. Admittance spectroscopy reveals that Sb₂Se₃ solar cells with Se seed layers have higher activation energies for defect states and significantly lower defect densities (1.2 × 10¹⁴, 2.7 × 10¹⁴, and 1.3 × 10¹⁵ cm⁻³ for D1, D2, and D3) compared to an order of magnitude higher densities in Sb₂Se₃ solar cells without a Se seed layer. First-principles calculations support these findings, showing that Se seed layers create a Se-rich environment, reducing selenium vacancies (V _Se), antimony on selenium sites (Sb _Se), and interface defects. This dual passivation mechanism suppresses defect formation and activation, increasing carrier concentration and open-circuit voltage (V _OC). Ultimately, employing this novel method, a V _OC of 498.3 mV and an efficiency of 8.42%, the highest performance reported for Sb₂Se₃ solar cells prepared via vapor transport deposition (VTD), are achieved.