New van der Waals Heterostructures Based on Borophene and Rhenium Sulfide/Selenide for Photovoltaics: An Ab Initio Study  
[PERSON]  
1 Institute of Physics, Saratov State University, Astrakhanskaya Street 83, 410012 Saratov, Russia;  
slepchenkovm@mail. Such structures, called van der Waals heterostructures, are obtained in practice using the technique of direct mechanical assembly (micromechanical superposition) [11], as well as chemical vapor deposition (CVD) [12] and physical epitaxy [13] methods. The created van der Waals heterostructures find their application in the development of nano- and optoelectronic devices, including field-effect tunneling transistors [14], memory devices [15], photodetectors [16], solar cells [17], and rechargeable batteries [18]. Photovoltaics is considered one of the most promising fields of application for van der Waals heterostructures. Certain successes have already been achieved in the field of creating solar cells based on TMD heterostructures, built mainly on the basis of well-studied molybdenum disulfide (MoS\({}_{2}\)) and molybdenum diselenide (MoSe\({}_{2}\)), as well as tungsten disulfide (WS\({}_{2}\)) and tungsten diselenide (WSe\({}_{2}\)) [19; 20; 21; 22; 23]. However, the photoelectric cells created on the basis of MoS\({}_{2}\) and WS\({}_{2}\) are mainly focused on operating in a narrow region of the visible range of the electromagnetic spectrum, and only slightly cover the region of the near-infrared range [24; 25; 26; 27]. At the same time, the emergence of new representatives of TMD, such as ReS\({}_{2}\), ReSe\({}_{2}\), TiS\({}_{2}\), TiSe\({}_{2}\), and HfS\({}_{2}\)[28; 29], exhibiting pronounced semiconductor properties, opens new possibilities in the direction of creating broadband photoelectric cells based on TMD. As is known, when constructing a layered heterostructure, the key point is the matching of the crystal lattices of the combined 2D materials. Borophene, which is currently being successfully synthesized, can be considered a promising material for creating new 2D heterostructures [30; 31]. Due to borophene polymorphism, various configurations of bonds between the boron atoms should relax the crystallographic lattice matching requirements for the combined 2D materials. In addition, the unique combination of properties of borophene, such as lightness, flexibility, mechanical strength, high conductivity, and optical transparency, makes it one of the most promising single-element 2D materials for nano- and optoelectronic purposes [32]. The first successes have already been achieved in the field of creating and studying borophene-based heterostructures. [PERSON] and [PERSON] [33] reported on the successful experimental implementation of vertical borophene/graphene heterostructures. During synthesis in an ultrahigh vacuum chamber, graphene was first grown on a Ag (111) metal substrate at a higher temperature, and then boron was deposited on the same substrate. Despite the imperfect crystallographic lattice and symmetry matching, the created graphene/borophene heterostructures have almost perfect atomic consistency. An alternative approach to obtaining vertical heterostructures based on borophene and graphene was proposed by [PERSON] et al. [34]. A new borophene/graphene heterostructure was obtained by heating a mixture of sodium borohydride and multilayer graphene, with the subsequent stepwise thermal decomposition of sodium borohydride, in situ in a high-purity hydrogen medium. Testing the humidity sensing behavior of the heterostructure under ambient conditions has shown that the borophene/graphene heterostructure exhibits high sensitivity (4200%) and a fast response/recovery time (10.5 s/8.3 s), with long-term stability and flexibility, which makes it suitable for creating highly efficient humidity sensors. Based on the results of ab initio calculations, [PERSON] et al.