Controlling Unintentional Defects Enables High‐Efficient Antimony Selenide Solar Cells

Abstract

Deep‐level defects in semiconductor materials usually induce carrier trapping and non‐radiative recombination. However, defects caused by unintentional contaminants in antimony selenide (Sb₂Se₃) solar cells have rarely been reported. Herein, the correlation between defect properties and unintentional impurities in the Sb₂Se₃ absorber is investigated, which is prepared by injection vapor deposition with Sb₂Se₃ source purities ranging from 99.9% to 99.9999%. The analysis of deep‐level transient spectra reveals that an increase in impurity concentration does not result in new defect types. Nevertheless, the higher impurity level causes an increase in both the defect density and the capture cross section of the original defect. To address this challenge, defect engineering is developed to regulate the growth of the Sb₂Se₃ absorber. This strategy completely suppresses deepest defect states E3, a mixture of intrinsic defect (Sb_Se) and impurity Si related defect. As a result, the carrier lifetime increases significantly from 0.37 to 3.4 ps. This enables to fabricate Sb₂Se₃ solar cells with a power conversion efficiency of 10.41%. This work uncovers the characteristics of unintentional contaminant‐related defects, and provides a strategy for fabricating highly efficient Sb₂Se₃ solar cells with low‐purity source materials.