We report a dual-mode organic photodetector (OPD) that has a trilayer visible light absorber/optical spacer/near-infrared (NIR) light absorber configuration. In the presence of NIR light, photocurrent is produced in the NIR light–absorbing layer due to the trap-assisted charge injection at the organic/cathode interface at a reverse bias. In the presence of visible light, photocurrent is produced in the visible light–absorbing layer, enabled by the trap-assisted charge injection at the anode/organic interface at a forward bias. A high responsivity of >10 A/W is obtained in both short and long wavelengths. The dual-mode OPD exhibits an NIR light response operated at a reverse bias and a visible light response operated at a forward bias, with a high specific detectivity of ~1013 Jones in both NIR and visible light ranges. A bias-switchable spectral response OPD offers an attractive option for applications in environmental pollution detection, bioimaging process, wellness, and security monitoring in two distinct bands.
The present band‐selective photodetection is realized by incorporating different optical filters with broadband photodetectors (PDs). However, the use of the optical filters reduces the overall PD sensitivity. This work reports on the effort to develop high‐performance filter‐free band‐selective organic photodetectors (OPDs) having a heterostructure photoactive layer architecture, comprising a semiconducting shorter‐wavelength light depletion layer and a bulk heterojunction (BHJ) layer with an extended absorption to longer wavelengths. The filter‐free band‐selective photodetection is realized by adjusting the difference in wavelengths between the transmission cut‐off wavelength of the semiconducting light depletion layer and the absorption edge of the BHJ layer. For example, a filter‐free visible‐blind near‐infrared OPD, with a spectral rejection ratio of 100, a high responsivity of 0.39 A W−1, a high −3 dB cutoff frequency of 80 kHz, and a fast response time of ≈7 µs, is demonstrated, offering an exciting option for a plethora of applications in imaging and light communications.
The presence of oxygen functional groups in GO enhances the charge storage behavior of Ce-MOF/GO composites for use as supercapacitor electrode materials.
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