The effect of imide substituents on the optical properties of perylene diimide derivatives

Abstract As one of the most important organic semiconductors, perylene diimide derivatives (PDIs) have been widely applied in optoelectronics. Two kinds of soluble PDIs with different imide substituents have been synthesized and their optical properties have been investigated. The photoluminescence (PL) intensity of the PDI with amino phenyl imide substituents (NH 2 ‐PDI) is much lower than that of the PDI with octyl imide substituents (O‐PDI). It can be found that the Stokes shift of O‐PDI is positive, whereas, the Stokes shift of NH 2 ‐PDI is negative. The emission intensity of the 0–0 electron transition relative to that of the 1–0 electron transition ( I 0–0 / I 1–0 ) in the PL spectrum of O‐PDI is decreased, but the value of I 0–0 / I 1–0 in the PL spectra of NH 2 ‐PDI is increased as the dielectric constant of the solvent increases. The large overlap between the absorption and PL spectra plays an important role to result in the low PL intensity of NH 2 ‐PDI. The PL decay data show that a non‐radiative process, photoinduced electron transfer, also contributes to the low PL intensity of NH 2 ‐PDI. The results can help researchers to understand the effect of the imide substituents on the optical properties of PDIs.