Fig. 1. Schematic diagram of the photothermoelectric (PTE) effect

Fig. 2. Typical flexible detection materials based on PTE effect

Fig. 3. Schematic diagram of CNT^[17]. (a) Schematic diagram of an SWCNT; (b) schematic diagram of an MWCNT

Fig. 4. Different types of CNTs flexible THz PTE detectors. (a) Schematic diagram of polarization-sensitive carbon nanotube PTE detector^[28]; (b) photograph of the curved CNT film and optical microscopy image of horizontally aligned CNTs^[28]; (c) omnidirectional image taken by multi-view scan of a syringe (a breakage on the syringe is detected without bulky components)^[29]

Fig. 5. CNT flexible PTE detectors for different applications. (a) Schematic diagram of high integrated π‑shaped pixel structure^[34]; (b) photo-induced voltage response as a function of the number of series PN junction of the present CNT film-based stretchable device^[35]; (c) non-destructive reflective multi-view stereoscopic photo-imaging inspection of capsules in a glass beverage bottle^[36]; (d) photos of stretchable broadband optical sensor array sheet^[37]

Fig. 6. CNT PTE detectors that can be sewn on a Polo shirt^[38]. (a) A carbon nanotube fiber detector sewn on the Polo shirt; (b)‒(c) the front and back of the detector, that is the outside and inside of the Polo shirt; (d) p⁺-p^- junction is located outside the Polo shirt, while the p^--p⁺ junction is hidden in the Polo shirt; (e) both ends of the detector are connected to an external circuit for measuring the induced light voltage; (f) I‑V characteristic curve, the curve moves upward under illumination

Fig. 7. CNT flexible PTE detector arrays fabricated with different alignment methods. (a) Schematic diagram of the self-aligned filtration process^[39]; (b) photograph of the all-printable CNT film flexible PTE imager^[40]; (c)‒(d) a knife image obtained by CNT flexible PTE imager^[40]

Fig. 8. Graphene PTE detectors fabricated by different methods. (a) Schematic diagram (left) and experimental photo (right) show photoresponse test of graphene flexible PTE detector, where the channel is composed of p-type (red) and n-type (blue) graphenes^[45]; (b) schematic illustration of the electrical characteristic measurement for the graphene detector under strain^[46]

Fig. 9. Schematic diagram of a suspended RGO photodetector and the effect of annealing temperature on its photoresponse^[47]

Fig. 10. Manufacturing process and structure diagram of LSG/CsPbBr₃ PTE detector^[53]. (a)‒(e) Manufacturing process; (f) structure diagram

Fig. 11. Flexible PTE detectors based on different inorganic compounds. (a)‒(c) Schematic diagram and flexibility test of Bi film flexible PTE detector^[60]; (d) image of HfTe₅ photodetectors in a flexed state^［61］; (e) photovoltage of the flexible HfTe₅ device at different bending radius^[61]; (f) photoresponse of SnTe PTE detector after different bending cycles^[64]

Fig. 12. Cs₃Cu₂I₅ flexible PTE detectors^[65]. (a) Photo of flexible PTE detector array under UV irradiation; (b) photo of flexible PTE detector array after bending; (c) process of imaging objects using detector array; (d) three-dimensional diagram shows the photocurrent on each pixel of the PTE detector array

Fig. 13. NbS₃ flexible PTE detectors^[19]. (a) Schematic of NbS₃-based PTE detector in a flexed state; (b) photo of NbS₃-based detector; (c) air stability measurement of NbS₃-based device

Fig. 14. Ti₃C₂T_x ink pen writes on different substrates^［75］. (a) Use a pen to draw pictures of four traditional Chinese plants on the surface of fabric, PS foam, wood and PE foam; (b) photos of fabric chips based on the ink with different widths

Fig. 15. Preparation process of thermoelectric fabric with double shell structure and demonstration of its flexibility and conductivity^[91]

Fig. 16. Flexible PTE detectors based on PDPP4T^[94]. (a) Imaging the letters “PTE” with PTE detector array; (b) sensing image of the array under 100 mW·cm^-2 light intensity; (c) photo of flexible PTE generator prototype; (d) output voltage and power of a typical PTE generator under the dark environment and 100 mW·cm^-2 white light intensity

Fig. 17. Flexible PTE detectors based on PTII and TzQI-TDPP^[100]. (a) p-channel thiophene isoindigo based homopolymer PTII and the synthesis of n-channel polymer TzQI-TDPP; (b) an illustration of PTE device configuration; (c) thin-film surface temperature under 1700 nm NIR laser irradiation

Fig. 18. Flexible PTE detectors based on [Cu_x(Cu-ett)]:PVDF^[102]. (a) Molecular structure of poly [Cu_x(Cu-ett)] and PVDF; (b) absorption spectra of three materials; (c)‒(e) schematic diagram of manufacturing process of PTE device

Fig. 19. Flexible PTE detectors based on colloidal plasmonic gold nanoparticles^[104]. (a) TEM image of Au NPs; (b) optical image of the flexible Au NPs-coated PEDOT:PSS/Ag₂Se hybrid PTE generators; (c)‒(d) voltage output of PEDOT:PSS/Ag₂Se hybrid optoelectronic devices coated with photothermal Au NPs prepared on polypropylene nonwovens

Fig. 20. Flexible PTE detectors based on graphene/PANI composite. (a) Photovoltage response of graphene/PANI PTE detectors under multiple excitation of finger spontaneous radiation (place the fingertip 3‒5 mm away from the photodetector in each cycle and move it vertically)^[110]; (b) flexible 8 pixel×8 pixel detector array on PET substrate^[110]; (c) schematic of the graphene/PEI detectors^[112]; (d) stable photocurrent of graphene/PEI detectors under multiple bending cycles^[112]

Fig. 21. Flexible PTE detectors based on PBI/MWCNT^[116]. (a) Schematic for the PTE characterization of PBI/MWCNT nanocomposite films under visible light irradiation and TEM image of PBI/MWCNT film; (b) time-dependent photothermal temperature increase (ΔT_PT), voltage generation (V_PTE), and electric current generation (A_PTE) changes of the PBI/MWCNT film at the edge under the visible light illumination with 520 nm and 8.87 W·cm^-2