Two-Dimensional Direct Semiconductor Boron Monochalcogenide γ-BTe: Room-Temperature Single-Bound Exciton and Novel Donor Material in Excitonic Solar Cells

Abstract

Recently, excitonic solar cells (XSCs) with high photovoltaic performance have raised research interests because of their high power conversion efficiencies (PCEs). Herein, by using first-principles calculations, we predict that γ-BX (X = S, Se, Te) monolayers are direct semiconductors with the band gaps of 2.94, 2.71, and 1.32 eV, respectively, and maintain semiconduction in the broad strain range of 0% ≤ δ ≤ 5%. The moderate direct band gap, high transport property, dramatically high absorption from visible to the ultraviolet region, and extraordinary excitonic behavior of monolayer γ-BTe, render it promising for next-generation optoelectronic and photovoltaic devices. By choosing monolayer GeP 2 as a proper acceptor material, the practical upper limit of PCE for the heterobilayers of γ-BTe/GeP 2 reaches up to 21.76% (22.95% under strain), comparable to typical heterobilayer solar cells, making it a competitive donor material for photovoltaic device applications.

Solar cells based on 2D Janus group-III chalcogenide van der Waals heterostructures

“…In addition, 7 of them have PCEs exceeding 20%. Particularly, the PCEs of Ga 2 STe/GaInS 2 (23.69%) and In 2 SeTe/InSe (23.54%) vdW heterostructures were found to be slightly higher than those of the predicted values of recently proposed β-PdTe 2 /WTe 2 (23.14%), 119 MoSeTe–WSeTe (22.99%), 97 γ-BTe/GeP 2 (22.95%), 105 and Te/WTe 2 (22.5%) 63 excitonic solar cells. Nevertheless, lower efficiencies were obtained experimentally for 2D vertical p–n junctions composed of MoS 2 /WS 2 (0.2%), 120 GaTe/MoS 2 (0.45%), 121 ReS 2 /ReSe 2 (0.48%), 122 and WSe 2 /h-BN/graphene (4.1%).…”

“…Furthermore, the obtained absorption coefficients are comparable to those previously reported for other 2D materials, such as Janus TMDs, 97 PtSSe, 43 and γ-BTe. 105 This indicates that the investigated monolayers are suitable for use in optoelectronic devices. High charge carrier mobility in solar cell materials facilitates the movement and separation of photogenerated e-h pairs, thus ensuring a high conversion efficiency.…”

“…Furthermore, the obtained absorption coefficients are comparable to those previously reported for other 2D materials, such as Janus TMDs, 97 PtSSe, 43 and γ-BTe. 105 This indicates that the investigated monolayers are suitable for use in optoelectronic devices.…”

W4PCl11monolayer: an unexplored 2D material with moderate direct bandgap and strong visible-light absorption for highly efficient solar cells

“…As highlighted with black star in Fig. 6(d), the potential solar-cell device composed of 2D W 4 PCl 11 /Bi 2 WO 6 heterojunction could have a PCE η as high as 21.64%, which is comparable to or even larger than those of recently reported heterojunction systems, such as Te/WTe 2 (22.5%), 24 TiNF/TiNCl (22%), 71 γ-BTe/GeP 2 (21.76%), 72 HfTeSe 4 /Bi 2 WO 6 (20.8%), 13 β-PdTe 2 /MoTe 2 (20.59%), 25 GeSe/SnS (18%), 73 bilayer phosphorene/MoS 2 systems (16–18%). 70 Therefore, our proposed W 4 PCl 11 /Bi 2 WO 6 heterojunction has the competitive advantage in the reported 2D heterojunction solar cells.…”

Two-Dimensional B4S Monolayer: A Highly Anisotropic Nonclassical System with Planar Tetracoordinate Sulfur Atoms and Polyene Boron Chains

“…Prospective objects in this regard are boron sulfides B n S ( n ≥ 1), which can exist in a form of various graphene-like polymorphic modifications (as an example, B 2 S 3 and B 3 S 4 nanosheets) and are currently being actively studied. − It can be expected that a boron environment, which is prone to a multicenter bonding, will also favor the formation of nonclassical sulfur derivatives. Planar tetracoordinate sulfur derivatives have not yet been studied, although the possibility of an existence of such type compounds has been experimentally confirmed using an example of a metal-containing complex with SMn 4 structural motif …”