Performance do trímero PDI-DPP-PDI como material aceitador em células fotovoltaicas orgânicas

Abstract

In this work, the PDI-DPP-PDI trimer was studied as an acceptor material in organic photovoltaic devices with PBDTTT-CT or PTB7-Th as donor polymers. These materials have a complementary absorption spectrum and, therefore, photovoltaic devices op those may present proper photon collection at the visible region of the solar spectrum. However, as cast BHJ devices produced with PBDTTT-CT: PDI-DPP-PDI or PTBT-Th: PDI-DPP-PDI ratio of 1:1.5 (v:v), result in an efficiency (ƞ) of 1.35 and 1.67%, respectively. The AFM results indicate that although there are agglomerated structures with size around 100 nm in the topography image, the phase image does not indicate phase separation of the order of micrometers, showing a better distribution of the PDI-DPP-PDI trimer in the active layer, when compared with other perylene derivatives molecules which tend to form isolated clusters of the order of 0.5-1 µm. In order to optimize the distribution of the trimer in the polymeric matrix and to obtain an increase in energy conversion efficiency, two procedures were adopted: 1) use of the chloronaphthalene (CN) additive and 2) solvent vapor annealing (SVA) chlorobenzene (CB) or tetrahydrofuran (THF). The use of the CN additive in the proportion 0.5% (v/v) did not result in significant changes in the morphology or improvement of the photovoltaic parameters. In the UV-Vis spectra of the films, it is verified that using both procedures (additive or SVA) it is verified that using both procedures (additive or SVA) there is variation in the relative intensity of the bands. These variations are related to different conformations / packagings of the polymer and / or molecule. The experimental conditions that resulted in higher efficiency devices produced with the active layer PBDTTT-CT: PDI-DPP-PDI in the proportion 1:1.5 using 10 mg/mL in CF as a solvent and exposure to SVA in CB for 10 minutes, resulting in short circuit current density (JSC) of 19.26 mA / cm2, open circuit voltage (VOC) of 0.88 V, fill factor (FF) of 29.9% and ƞ of 5.08%.