Fig. 1. BP and b-AsP photodetectors. (a) Crystal structure of BP^[36]; (b) Modulation of the bandgap of BP by electrical field^[38]; (c) Modulation of the photoresponse of BP by electrical field^[37]. Modulation of the bandgap and photoresponse of BP by strain^[39]: (d) Modulation of photoluminescence by strain; (e) Schematic of the BP photodetector on PETG flexible substrate; (f) Photoresponsivity vs wavelength and strain. b-AsP photodetector^[42]: (g) Absorbance spectrum of b-AsP with 17% P; (h) Photoresponsivity and EQE vs wavelength

Fig. 2. Photodetectors based on transition metal chalcogenides. (a) Photoresponse spectrum of MoTe₂ photodetector^[51]; (b) Enhancement factor vs wavelength of the Au hollow nanorod enhanced MoTe₂ photodetector^[52]. PtSe₂ photodetector^[54]: (c) Crystal structure of PtSe₂; (d) Dynamic photoresponse of monolayer PtSe₂ photodetector; (e) Dynamic photoresponse of bilayer PtSe₂ photodetector; (f) Bandgap of PtSe₂ vs defect concentration

Fig. 3. Te nanosheet photodetector. (a) Crystal structure of Te^[66]. Photodetector based on Te nanosheet from hydrothermal synthesis^[67]: (b) Schematic of the photodetector; (c) Photoresponsivity vs wavelength and laser power; (d) Anisotropic photoresponse when irradiated by 2.3 μm light. Photodetectors based on Te nanostructures synthesized from chemical vapor deposition^[68]: (e) Photoresponse of nanowire and nanosheet detector to black body irradiation; (f) Anisotropic photoresponse of nanosheet detector

Fig. 4. Bi₂O₂Se photodetector. (a) Crystal structure of Bi₂O₂Se^[69]. Performance of Bi₂O₂Se photodetector^[70]: (b) Photoresponse spectrum and absorbance spectrum; (c) Photoresponsivity vs bias voltage and light power; (d) Response time

Fig. 5. Heterostructure photodetectors. Avalanche photodetector based on InSe/BP heterostructure^[72]: (a) Device structure; (b) Schematic of ballistic avalanche; (c) Photoresponse. Interlayer exciton photodetector based on WS₂/HfS₂ heterostructure^[73]: (d) Device structure; (e) Current vs voltage under light irradiation; (f) Specific detectivity vs wavelength. Unipolar barrier photodetector based on BP/MoS₂/graphene heterostructure^[28]: (g) Device structure; (h) Band structure under reverse bias; (i) Specific detectivity vs wavelength

Fig. 6. Waveguide photodetector. Photodetector based on MoTe₂ with left and right electrodes configuration^[74]: (a) Device structure; (b) Dynamic response; (c) Eye diagram (1 Gbit/s). Photodetector based on MoTe₂ with top and down electrodes configuration^[75]: (d) Device structure; (e) Dynamic response of the photodetector with 11 nm thick MoTe₂. Photodetector based on strained MoTe₂^[76]: (f) Device structure; (g) Device picture; (h) Schematic of the formation of strain in the device