Antimony selenide (Sb2Se3) is an emerging material for photovoltaic applications that has recently enabled solar cells with a 9.2% power conversion efficiency. Device and material design is based on the assumption that Sb2Se3 is a p-type semiconductor where the majority of charge carriers are holes. Sb2Se3 is therefore often interfaced with n-type materials to obtain efficient charge separation and maximize device efficiency. Recent works, however, challenge this assumption, suggesting that Sb2Se3 can have either an n-type or an intrinsic character. Now, Jonathan Major and colleagues across the UK, United States and France verify the intrinsic nature of Sb2Se3 and report on its use as a photovoltaic absorber with n-type character.
The researchers investigate the type of majority carriers, that is, electrons or holes, in Sb2Se3 by means of a range of complementary techniques. They find that the high-quality Sb2Se3 behaves as an intrinsic material with no detectable dominant carrier type. However, impurities in the precursor materials can lead to either n- or p-type Sb2Se3, thus offering an explanation for the opposite results reported in literature. Furthermore, Major and colleagues demonstrate solar cells based on n-type Sb2Se3 with efficiency over 7%, equalling p-type counterparts. The researchers suggest that future investigations should exploit the opportunity to dope Sb2Se3 at will to understand which carrier type and device design maximize solar cell performance.
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Tregnago, G. Tested for doping. Nat Energy 5, 357 (2020). https://doi.org/10.1038/s41560-020-0628-3