Novel BCN-phosphorene bilayer: Dependence of carbon doping on band offsets for potential photovoltaic applications

Abstract

Two-dimensional van der Waals heterostructures (vdWHs) have rapidly become a paradigm shift in designing high-performance electronic and optoelectronic devices. Based on the density functional theory calculations, this work presents the electronic and optical properties of novel vdWHs constituted by ternary BCxN (x = 0, 2, and 6) and black phosphorene (BlackP). The findings reveal that BN-BlackP and BC2N-BlackP hybrids exhibit straddling type-I band offset, whereas BC6N-BlackP adopts staggered type-II. This compositional dependence on band alignment is ascribed to the reduction in band gaps of BCxN upon increasing carbon concentration. The hybrids also show modulation in band gaps and band alignments caused by the external electric field due to the Stark effect. Their gaps do not only drop with the increasing field magnitude, but the band alignments also get changed. Moreover, the resultant type-II offset of BC6N-BlackP leads to further investigation into its photovoltaic application because of the spatial electron-hole decoupling. This vdWH enhances solar absorption in the majority infrared region, yielding the efficient solar-to-electricity conversion with the theoretical power conversion efficiency (PCE) up to 22.0%. The essential gate-tunabilty and exceptional PCE clearly demonstrate the feasibility of exploiting BCxN-BlackP vdWHs as a building block in electronic and photovoltaic devices. © 2019 Elsevier B.V.