Spectral response tuning and realization of quasi-solar-blind detection in organic ultraviolet photodetectors

A silane-containing triazine derivative (NSN) with ultrawide bandgap and excellent thermal stability was used as electron acceptor for organic ultraviolet photodetectors. Poly (9,9-dihexylfluorene-2,7-diyl) (PFH), 4,4′,4′′-tris(3-methylphenylphenylamino)-triphenylamine (m-MTDATA), 2,7-bis(3′,5′-diphenylphenyl)-9,9-diphenylfluorene (PFP) and poly(N-vinylcarbazole) (PVK) were applied as electron donors and respectively combined with NSN to construct planar heterojunction devices: indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)/donor/NSN/LiF/Al. Under illumination through the ITO electrode, though all the devices exhibit near-ultraviolet (NUV) response, the cutoff wavelength can be well tuned by selecting donors with different bandgaps. If a semitransparent Al cathode is applied for the incidence of light, the response region can be further extended to deep-ultraviolet (DUV) region. Particularly for PFP/NSN and PVK/NSN based devices, quasi-solar-blind response can be realized by combining home-made NUV-blocking organic filters. As a result, the devices are capable of NUV and DUV-selective response for radiation, respectively from ITO and Al sides. The study shown here may provide a useful guideline to achieve low-cost organic detectors with spectral selective response.