Miliaieva, D.

Nadaždy, V.

Koltsov, M. A.

Lopez, C.

Saeeyekta, H.

Kuliček, J.

Cazorla, C.

Saucedo, E.

Grzibovskis, Raitis

Vembris, Aivars

Krunks, Malle

Spalatu, Nicolae

Daria Miliaieva, Vojtech Nadazdy, Mykhailo Koltsov, Cibrán López, Hanieh Saeeyekta, Jaroslav Kuliček, Claudio Cazorla, Edgardo Saucedo, Raitis Grzibovskis, Aivars Vembris, Malle Krunks, Bohuslav Rezek and Nicolae Spalatu

Journal of Physics Energy

Institute of Physics

vol. 7, 3

2025

art. 035012

https://doi.org/10.1088/2515-7655/add59f

2515-7655

One of the reasons chalcogenide-based photovoltaic solar cells do not yet meet the expected high-power conversion efficiencies is a lack of understanding of their electronic structure, and particularly the nature of the point defects in the absorber materials. We show that the density of states (DOS) of the characteristic features of the electronic structure, such as band edges and energy distribution of defects, can be obtained experimentally by energy-resolved electrochemical impedance spectroscopy (ER-EIS) in a technically simple and quick way. The ER-EIS data correlate well with theoretical density functional theory (DFT) calculations. The ER-EIS reveals that Bi2S3, has only shallow defects near the conduction band minimum (CBM). In Sb2S3, ER-EIS also shows deep defect states, which can be the cause of the low electrical conductivity of Sb2S3 and lower than theoretically possible power conversion efficiency of Sb2S3-based solar cells. A dominant sulphur vacancy defect was identified in Bi- and Sb-chalcogenides. In the (SbxBi(1-x))2S3 ternary alloy series, a gradual transformation of CBM and defect states in the band gap was observed. Notably, a 1:9 ratio of Bi:Sb cations already transforms the deep sulphur defects into shallow ones while keeping the band edges similar to those of the pristine Sb2S3. It can provide a novel strategy for healing the deep defect states in Sb2S3, a crucial step for boosting solar cell performance.

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