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Quasiparticle electronic structure and optical spectra of single-layer and bilayer PdSe2: Proximity and defect-induced band gap renormalization
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. College of Chemistry and Chemical Engineering, Henan University, Kaifeng, Henan, 475004, China.ORCID iD: 0000-0002-1763-9383
2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 24, article id 245114Article in journal (Refereed) Published
Abstract [en]

The fundamental properties of recently synthesized single- and bilayer PdSe2 are investigated using accurate many-body perturbation GW theory to quantitatively examine their electronic structure and explain the insufficiency of previously reported experimental and theoretical results. Including electron-hole interactions responsible for exciton formation, we solve the Bethe-Salpeter equation on top of the GW0 approximation to predict the optical properties. The fundamental quasiparticle band gaps of single- and bilayer PdSe2 are 2.55 and 1.89 eV, respectively. The optical gap of monolayer PdSe2 reduces significantly due to a large excitonic binding energy of 0.65 eV comparable to that of MoSe2, while an increase of the layer number decreases the excitonic binding energy to 0.25 eV in bilayer PdSe2. The giant band gap renormalization of ∼36-38% in the bilayer (BL) PdSe2/graphene heterostructure has a high impact on the construction of PdSe2-based devices and explains the experimentally observed band gap. The small value of the experimental optical gap of single-layer (SL) PdSe2 (1.3 eV) can be explained by the presence of Se vacancies, which can drop the Tauc-estimated optical gap to ∼1.32 eV. The absorption spectra of both mono- and bilayer PdSe2 cover a wide region of photon energy, demonstrating promising application in solar cells and detectors. These findings provide a basis for a deeper understanding of the physical properties of PdSe2 and PdSe2-based heterostructures.

Place, publisher, year, edition, pages
American Physical Society, 2019. Vol. 99, no 24, article id 245114
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Physical Sciences
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URN: urn:nbn:se:kth:diva-262630DOI: 10.1103/PhysRevB.99.245114ISI: 000470840400005Scopus ID: 2-s2.0-85069720865OAI: oai:DiVA.org:kth-262630DiVA, id: diva2:1361501
Note

QC 20191016

Available from: 2019-10-16 Created: 2019-10-16 Last updated: 2019-10-16Bibliographically approved

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Ågren, Hans

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