Fig. 1. (a) Schematic diagram of 3D perovskite and 2D Ruddlesden–Popper perovskite structures; (b)–(d) schematic diagram of process for preparing (PEA)2PbBr4 microwire crystals by imprinting; (e)–(g) regioselective ion exchange preparation of (PEA)2PbBr4–(PEA)2PbBr4−xIx lateral heterojunction.

Fig. 2. (a) SEM image of the lateral heterojunction array; (b) I, Pb, Br element distribution of lateral heterojunction; (c)–(e) fluorescence microscope photos of lateral heterojunction array; (f) absorption spectrum, (g) XRD pattern, and (h) Raman spectrum of (PEA)2PbBr4−xIx, (PEA)2PbBr4, and (PEA)2PbI4; (i) typical time-resolved photoluminescence curves of (PEA)2PbBr4 and (PEA)2PbBr4−xIx.

Fig. 3. (a) Color plot of TA spectra from (PEA)2PbBr4; (b) TA spectra at 398–410 nm; (c) TA kinetics probed at a selected wavelength of 405 nm from (a); (d) color plot of TA spectra from (PEA)2PbBr4−xIx; (e) TA spectra at 498–545 nm; (f) TA kinetics probed at a selected wavelength of 518.9 nm from (d).

Fig. 4. (a) Sketch of a lateral heterojunction photodetector based on (PEA)2PbBr4−(PEA)2PbBr4−xIx; (b) I-V curve of PD under different light intensities; (c) I-t curve of the PD under different intensities of on–off light irradiation and 5 V bias; (d) variation of photocurrent and R with light intensity under 5 V bias; (e) I-t curve of PD under different on–off light intensities and 0 V bias; (f) under 0 V bias, the photocurrent and R versus light intensity.

Fig. 5. (a) Sketch of polarized light detection by the lateral heterojunction-based photodetector; (b) I-t curve of PD under light irradiation of different polarization angles; (c) photocurrent dependence on the polarization angle of the incident light. When the incident light rotates in the plane of the heterojunction: (d) photocurrent dependence on the angle of the incident light; (e) I-t curve of PD under the illumination of different incident angles. When the incident light rotates in the plane perpendicular to the heterojunction: (f) photocurrent dependence on the incident light angle; (g) I-t curve of PD under light irradiation at different incident angles.

Fig. 6. (a), (b) Photocurrent change curves of PD under different bending states; (c), (d) PD performance after different bending cycles; (e), (f) PD performance after storage in air for different times.

Fig. 7. (a) SEM image of a PDMS template with a microscale striped structure. (b) AFM image of (PEA)₂PbBr₄ microwire crystals. (c) Fluorescence microscope photograph of (PEA)₂PbBr₄ microwire crystals. (d) SEM image of the cross-section of (PEA)₂PbBr₄ microwire crystals.

Fig. 8. (a) Mapping of element I after 7 days. (b) Mapping of element Br after 7 days. (c)–(e) Fluorescence microscope images of heterogeneous junctions after 7 days.

Fig. 9. (a) Dark current of the device at a bias voltage of 5 V. (b) Variation curves of D and EQE of the device under different incident light intensities at a bias voltage of 5 V. (c) Dark current of the device at a bias voltage of 0 V. (d) Variation curves of D and EQE of the device under different incident light intensities at a bias voltage of 0 V.

Table 1. Performance of Perovskite–Perovskite Heterojunction-Based Photodetectors