Nature Materials, Published online: 27 August 2025; doi:10.1038/s41563-025-02313-8Sonochemical exfoliation of black phosphorus crystals with a slightly enlarged lattice parameter along the armchair direction produces narrow black phosphorus nanoribbons (BPNRs) with well-defined edge chirality at a yield of up to 95%. The high performance of transistors and photodetectors fabricated with these BPNRs demonstrates the potential of BPNRs for electronic and optoelectronic applications.