Abstract
•Spectral and ASE properties of MDMO-PPV in different solvents and concentrations.•Spectral and ASE properties of MDMO-PPV compared with MEH-PPV.•MDMO-PPV produced ASE due to vibronic transitions.•MDMO-PPV and MEH-PPV have an excellent optical gain and photochemical stability.
In this work, the photophysical properties of a conjugated polymer poly [2-methoxy-5-(3′,7′-dimethyloctyloxy) (MDMO-PPV) under a wide range of solvents and concentrations were studied. MDMO-PPV in tetrahydrofuran (THF) showed two absorption bands at 333 and 490 nm. Regardless of the optical density, the absorption spectrum did not change with increasing or decreasing the concentration. Consequently, the studies showed that the aggregations were not formed in the ground state for MDMO-PPV for all solvents and concentrations used. On the other hand, the fluorescence spectrum of MDMO-PPV in THF showed two distinctive bands around 555 and 595 nm. By increasing concentration, the profile of the fluorescence spectrum remained constant. Most of PPV derivatives’ spectra are affected by the concentrations and temperatures in the ground or excited states. Nevertheless, the ratio of the intensity bands (555 nm: 595 nm) MDMO-PPV was not significantly affected by the concentration or temperature in both cases. According to our knowledge, the band at 595 nm is not attributed to the excimeric state. Therefore, fluorescence bands 555 and 595 nm are composed of two vibronic transitions and assigned to 0–0, 0–1 respectively. Under pulsed laser excitation of Nd: YAG laser (λex = 355 nm), MDMO-PPV produced an amplified spontaneous emission (ASE) peaks at 597 nm. The ASE peaks may be attributed to 0–1transition.