Dynamic characterization of green-sensitive organic photodetectors using non-fullerene small molecules: Frequency response based-on the molecular structure

Abstract: The frequency response induced from the dynamic electrical parameters in the green-sensitive organic photodetectors (OPDs) using non-fullerene small molecules are investigated. In two OPDs comprising N,N-dimethyl quinacridone (DMQA) as a same donor and dibutyl-substituted dicyanovinyl terthiophene (DCV3T) or Boron-subphthalocyanine chloride (SubPc) as respective acceptors, the device B (DMQA/SubPc) shows a faster frequency response of 148.3 kHz than 92.9 kHz of device A (DMQA/DCV3T) at the applied voltage of -5 V. The low resistance is due to the combined effect of high mobility and high carrier concentration, and the low capacitance is influence from the dielectric constant, which is related with the theoretical parameters of reorganization energy and polarizability. The lower reorganization energy of SubPc might originate from its fused structure as compared with the conjugated backbone structure with conformational torsion points of DCV3T. On the contrary of isotropic geometry of SubPc, the linear structure of DCV3T may promote packing in the linear direction, so the polarizability could be maintained in bulk state resulting to the high dielectric constant. For high dynamic response of OPD, the molecular structure is proposed as a fused aromatic structure for high carrier mobility of the device and a molecular geometric isotropy for low dielectric constant.