Quasi-one-dimensional nanoribbons (NRs) are promising candidate materials for flexible optoelectronics with high device density. The optical properties of nanomaterials are strongly influenced by excitons, and it is important for flexible devices to explore how excitons behave under strain. In this work, we investigate the electronic and excitonic properties of bent black phosphorus (BP) NRs via density-functional theory and many-body Green's function methods. We find that inhomogeneous strain fields affect not only the first excitonic energy and thus the optical gap, but also the spatial distribution of the excitons. In particular, excitonic funnels can occur in bent black phosphorus nanoribbons (BPNRs), which drive higher-energy excitons toward lower energy locations. The funnels can be effectively tuned by the intensity and sign (compressed to tensile) of the strain field. Another critical factor is anisotropy: the funnel effect is much more pronounced in armchair BPNRs than in zigzag BPNRs. In addition, we find that the excitonic funnel effect in two-dimensional monolayer BP differs from that in multilayer BP films.

准一维纳米带（NRs）是具有高器件密度的柔性光电器件的有前途的候选材料。纳米材料的光学性质受到激子的强烈影响，因此对于柔性器件而言，探索激子在应变下的行为方式非常重要。在这项工作中，我们通过密度泛函理论和多体格林函数方法研究了弯曲的黑磷（BP）NRs的电子和激子性质。我们发现，不均匀的应变场不仅影响第一激子能量，进而影响光学间隙，还影响激子的空间分布。特别是，激子漏斗会出现在弯曲的黑磷纳米带（BPNRs）中，这会驱使高能激子流向能量较低的位置。漏斗可以通过应变场的强度和符号（压缩为拉伸）进行有效调整。另一个关键因素是各向异性：扶手椅形BPNR中的漏斗效应比之字形BPNR中的漏斗效应更为明显。此外，我们发现二维单层BP膜中的激子漏斗效应与多层BP膜中的激子漏斗效应不同。