Self‐Powered Photodetection and Optical Information Recognition in a Mixed‐Dimensional WSe 2 /CdSe Heterojunction

ABSTRACT Mixed‐dimensional van der Waals heterojunctions offer opportunities for self‐powered optical sensing and information processing, yet identifying the spatial origin of zero‐bias photoresponse remains important for understanding device operation. Here, a vertical WSe 2 /CdSe heterojunction composed of a WSe 2 nanosheet and a CdSe nanobelt is investigated for visible photodetection. Under 610 nm illumination, the device exhibits a photovoltaic response with an open‐circuit voltage of 0.403 V and a short‐circuit current of 4.77 × 10 −10 A. Quantitative photocurrent mapping reveals a mean response of 5.94 nA in the heterojunction overlap region, approximately 50 times that near the metal contacts. Scanning Kelvin probe microscopy yields a reproducible contact‐potential‐difference contrast of 293 ± 15 mV, whereas electronic‐structure calculations support a type‐II band‐edge configuration and interfacial charge redistribution. At 100 Hz, the measured rise/fall times are 1.09/0.99 ms at 0 V and 165/191 μs at +3 V. Under +3 V bias, approximately 97% of the reference modulation amplitude is retained at 1 kHz. Self‐powered optical imaging and wavelength‐ and time‐window‐dependent 8‐bit information recognition are further demonstrated, with all 96 tested bits correctly decoded. These results highlight the potential of mixed‐dimensional WSe 2 /CdSe heterojunctions for self‐powered visible‐light sensing and optical information recognition.