Improving the spectral response of amorphous Se photodetectors using organic semiconductors

We demonstrate a heterojunction amorphous Se (a-Se)/organic semiconductor photodetector that extends the long wavelength spectral response of pure a-Se devices from a cutoff of about 500 nm to 1000 nm. We show that a-Se/organic interfaces behave similarly to organic/organic interfaces in terms of energy level alignments and organic exciton dissociation. Due to the large ionization potential of a-Se (5.7 eV), organic materials with similarly large ionization potentials are required for hole injection into a-Se and possible avalanche multiplication.