Filter-free tunable spectrum photodetectors

A filter-free tunable spectrum photodetector comprising a layered structure of at least two electrodes and at least two functional layers, wherein a first functional layer of the at least two functional layers comprises a shorter-wavelength electromagnetic wave depletion layer within a first wavelength range of 10 nm to 1000 μm, wherein the first functional layer absorbs electromagnetic radiation in the first wavelength range without generating photocurrent and is transparent to electromagnetic radiation in a longer-wavelength second wavelength range of 10 nm to 1000 μm, and wherein a second functional layer of the at least two functional layers comprises a longer-wavelength electromagnetic wave absorbing layer within the second wavelength range for generating photocurrent upon absorption of the longer-wavelength electromagnetic waves and wherein filter-free tunable spectral detection of the photodetector occurs by adjusting a selected spectral response window within a wavelength range determined by a difference in wavelength between a transmission cut-off wavelength of the first functional layer and an absorbing edge of the second functional layer.