Study of the Optoelectronic Properties of Bi2S3 as a Nesting-Like Band Gap Semiconductor
Wojciech Linhart a, Szymon Zelewski a, Paweł Scharoch a, Filip Dybała a, Robert Kudrawiec a
a Department of Semiconductor Materials Engineering, Faculty of Fundamental Problems of Technology, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS23 & Sustainable Technology Forum València (STECH23) (MATSUS23)
#2DSUSY - 2D Nanomaterials for Sustainable Energy
València, Spain, 2023 March 6th - 10th
Organizers: Maria Antonia Herrero Chamorro and Maurizio Prato
Poster, Wojciech Linhart, 320
Publication date: 22nd December 2022

Bismuth sulfide (Bi2S3) is a non-toxic metal chalcogenide semiconductor, which lies in the optimal of the solar spectrum with a band gap varying in the range from 1.3 to 1.7 eV, without conclusive evidence of the origin of this deviation [1]. It has a high absorption coefficient and a conversion efficiency from an incident photon to an electron value of ∼5% [2,3]. Under ambient conditions, Bi2S3 has an orthorhombic structure and has a layered (lamellar) structure. This van der Waals material is a potential solar absorber, but its optoelectronic properties are not fully explored and understood.

Here, the optical properties of bulk Bi2S3 have been comprehensively investigated by temperature-dependent optical absorption, photoreflectance (PR) and photoluminescence (PL) measurements in the 20-300 K temperature range and also in the hydrostatic pressure 0 - 20 kbar. The fundamental absorption edge and the photoreflectance transition value has been found to be ∼1.30 eV at room temperature, which is the optimal value, giving a maximum conversion efficiency according to the Shockley–Queisser limit for a single-junction solar cell. The total energy change of the fundamental band gap between 10 K and 300 K is significant of ~0.16 eV, compared to conventional semiconductors. The combination of experimental methods clearly shows that the direct optical transition dominates over the indirect one. Therefore, we reveal Bi2S3 as a nesting-like band gap semiconductor with a strong absorption edge and excitonic emission [4]. A careful analysis of the band structure shows that the experimental results are very consistent with the DFT calculations.

W. M. L. acknowledges support from the Polish National Science Center (Grant No. 2019/35/B/ST5/02819).

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