Síntese e caracterização de nanopartículas para aplicação em dispositivos orgânicos conversores de luz

Abstract

Nanoparticles (NPs) from the polymer poly[3-hexylthiophene] (P3HT) and the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) were synthesised by the miniemulsion method and the nanoprecipitation method. The aim of synthesising these NPs is to avoid the usage of toxic solvents that are not environmentally friendly in the fabrication of organic solar cells by producing non-toxic colloidal suspensions. By the miniemulsion technique, NPs constituted by P3HT, PC61BM, and the blend P3HT:PC61BM were synthesised, while NPs of P3HT, PC61BM, P3HT:PC61BM, and NPs with a core-shell structure with P3HT as the core and PC61BM as the shell were obtained by the nanoprecipitation method. SiO2 NPs were also produced via the Stöber method to be inserted into P3HT:PC61BM photoactive layers or as a monolayer over the transparent electrode in organic photovoltaic devices (OPVs), with the intention of increasing the conversion efficiency of these devices through the light-trapping effect. The organic NPs were characterised by dynamic light scattering (DLS) and presented sizes from 159 to 312 nm, while SiO2 NPs presented diameters of 266,8 and 402,7 nm. UV-Vis absorption spectroscopy was employed to investigate the changes in the light radiation absorption by the organic NPs, both in colloidal suspension and thin films, compared to source materials in solution. UV-Vis absorption spectra were also helpful to compare P3HT:PC61BM with and without the insertion of SiO2 NPs in their matrix, to understand the influence of these NPs on the electronic structure of the films. The same technique was also applied to evaluate the transmittance of the SiO2 NPs monolayer deposited over the semi-transparent electrode. Photoluminescence (PL) spectroscopy was employed to investigate the suppression of PL when the electron-donating material (P3HT) comes into contact with the electron-accepting material (PC61BM). Images of the NPs synthesised in this work were obtained by transmission (TEM) and scanning (SEM) electron microscopy. OPV devices employing the organic NPs as the photoactive layer and devices with SiO2 NPs dispersed in P3HT:PC61BM thin films as the active layer were fabricated and electrically characterised by current density-voltage curves (J-V) under illumination to obtain parameters related to their photovoltaic effects.