Theoretical and experimental study of PTDPV optical and vibrational properties and its application in white electroluminescent blends

Abstract

The polymer Poly[tris(2,5-bis(hexyloxy)-1,4-phenylenevinylene)-alt-(1,3-phenylenevinylene)] (PTDPV) has a broad range of visible emission extending from green to red, and thus may be useful for obtaining a white light emitting blend. Nevertheless, the amount of works found in the literature dealing with the optical emission properties of PTDPV is very small. In this work, we performed a study of the optical properties of this material using photoluminescence and of the vibrational properties using Raman and Fourier Transform Infrared Spectroscopy (FT-IR) techniques. At the same time, we use the Density Functional Theory (DFT) method to calculate the optical, vibrational and molecular properties of PTDPV. We have obtained the best DFT results using a hybrid functional and a simple basis set (DFT / B3LYP and 6–31 g *), without addition of correction or polarization factors (+). To reach these conclusions, we compared the HOMO and LUMO values obtained via DFT with those found in the literature. Furthermore, the Raman and IR simulations obtained using this basis set were compared with the experimental results of the PTDPV, showing great agreement. From the vibrational modes obtained, it was possible, using the Lin model [1–3], based on the Franck Condon approximations, to reconstruct the photoluminescence spectrum of the PTDPV. Based on these reconstructed spectra, it was possible to establish the contribution of the different vibrational modes to the vibronic emissions of the photoluminescence spectrum. The quality of the reconstruction obtained with the DFT results and that obtained with the experimental ones are very close, showing the possibility of using in this reconstruction the calculated vibrational modes when the experimental ones are not available. To demonstrate the application of this material, PFO:PTDPV blends were prepared, with which white photoluminescence was obtained. OLEDs prepared with these blends, in suitable proportions, emitted white light using low excitation power, demonstrating the feasibility of using PTDPV in OLEDs for lighting, which could be prepared by solution on large areas.