Filter‐Free Band‐Selective Organic Photodetectors

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. A high‐performance filter‐free near‐infrared (NIR) organic photodetector (OPD), with a bilayer visible‐light depletion layer/NIR‐absorbing layer photoactive layer architecture, offers an inspiring option for application in light communications. The detection window of the band‐selective OPD is determined by the difference in wavelengths between the transmission cut‐off wavelength of the visible‐light depletion layer and absorbing edge of the NIR‐absorbing layer.