Highly efficient heterojunction solar cells enabled by edge-modified tellurene nanoribbons.

Tellurene, a two-dimensional (2D) semiconductor, meets the requirements for optoelectronic applications with desirable properties, such as a suitable band gap, high carrier mobility, strong visible light absorption and high air stability. Here, we demonstrate that the band engineering of zigzag tellurene nanoribbons (ZTNRs) via edge-modification can be used to construct highly efficient heterojunction solar cells by using first-principles density functional theory (DFT) calculations. We find that edge-modification enhances the stability of ZTNRs and halogen-modified ZTNRs showing suitable band gaps (1.35-1.53 eV) for sunlight absorption. Furthermore, the band gaps of ZTNRs with tetragonal edges do not strongly depend on the edge-modification and ribbon width, which is conducive to experimental realization. The heterojunctions constructed by halogen-modified ZTNRs show desirable type 2 band alignments and small band offsets with reduced band gaps and enhanced sunlight absorption, resulting in high power conversion efficiency (PCE) in heterojunction solar cells. In particular, the calculated maximum PCE of designed heterojunction solar cells based on halogen-modified ZTNRs can reach as high as 22.6%.