A new wide bandgap organic semiconductor and its application in organic UV sensors with tunable response wavelength

A triphenylbenzene-containing carbazole derivative (PCP) with wide bandgap, good hole mobility, and excellent thermal stability was synthesized and used as electron donor to construct planar heterojunction organic ultraviolet sensors (UVSs), while bis(4-(4,6-diphenyl-1,3,5-triazine-2-yl)phenyl)diphenylsilane (NSN) was used as electron acceptor. The UVS ITO/PEDOT:PSS/PCP/NSN/LiF/Al/Ag showed good responses to illumination from both ITO and cathode sides. When a semitransparent cathode was applied, the response region could be further extended to deep-ultraviolet (DUV) region. When the semitransparent Al (9 nm)/Ag (30 nm) cathode was replaced by Al (13 nm), the blue-shift of the response spectra of the UVS could be found. It was especially interesting that the cutoff of response could be changed by using different kind of cathodes. This study may provide a useful guideline to achieve low-cost organic deep-ultraviolet sensors (DUVSs) with tunable spectral response.