Optical properties of thin flms of MEH-PPV produced by the spin-coating technique at different rotational speeds

We present a study on the optical properties of thin flms of poly[2-methoxy-5-(20-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) produced at a concentration of 10 mg/ml xylene. The solution was deposited onto glass substrates by the spin-coating technique at different rotational speeds (300, 1000 and 4000 rpm). We study the effect of rotational speeds on the sample at 300 K, by analyzing the photoluminescence (PL) spectra at different points of the polymeric flm. We also analyze the effects of the excitation power on the optical behavior of MEH-PPV at 300 K. At low temperatures the PL spectra of sample A1000 (1000 rpm) show a narrow peak for the electronic transition and a series of vibronic sidebands which reveal the electron coupling with two different vibronic modes. In the temperature range of 130 K to 290 K, we analyze systematically the transition lineshapes in the optical spectra using Gaussian curves.