Improvement of Exciton Collection and Light-Harvesting Range in Ternary Blend Polymer Solar Cells Based on Two Non-Fullerene Acceptors

Abstract

A non-fullerene molecule named Y6 was incorporated into a binary blend of PBDB-T and IT-M to further enhance photon harvesting in the near-infrared (near-IR) region. Compared with PBDB-T/IT-M binary blend devices, PBDB-T/IT-M/Y6 ternary blend devices exhibited an improved short-circuit current density (JSC) from 15.34 to 19.09 mA cm−2. As a result, the power conversion efficiency (PCE) increased from 10.65% to 12.50%. With an increasing weight ratio of Y6, the external quantum efficiency (EQE) was enhanced at around 825 nm, which is ascribed to the absorption of Y6. At the same time, EQE was also enhanced at around 600–700 nm, which is ascribed to the absorption of IT-M, although the optical absorption intensity of IT-M decreased with increasing weight ratio of Y6. This is because of the efficient energy transfer from IT-M to Y6, which can collect the IT-M exciton lost in the PBDB-T/IT-M binary blend. Interestingly, the EQE spectra of PBDB-T/IT-M/Y6 ternary blend devices were not only increased but also red-shifted in the near-IR region with increasing weight ratio of Y6. This finding suggests that the absorption spectrum of Y6 is dependent on the weight ratio of Y6, which is probably due to different aggregation states depending on the weight ratio. This aggregate property of Y6 was also studied in terms of surface energy.

Heteroleptic Ruthenium(II) Complexes with 2,2′-Bipyridines Having Carbonitriles as Anchoring Groups for ZnO Surfaces: Syntheses, Physicochemical Properties, and Applications in Organic Solar Cells

“…The second effect is related to the fact that the EQE for the ZnO/Ru­(II) samples have a dip at the maximum of absorption (Figure b). While some fraction of this fact might be related to changes in microstructure, ,,− we believe that the major role is played by the optimum thickness being different for the samples with and without Ru­(II) complexes. In particular, for the latter, the active layer is thicker (19 mm/s compared to 73 mm/s for the reference), leading to the so-called filtering effect in the EQE .…”

Pronounced Backbone Coplanarization by π-Extension in a Sterically Hindered Conjugated Polymer System Leads to Higher Photovoltaic Performance in Non-Fullerene Solar Cells

“…Both blend films gave similar absorptions corresponding to Y6 in the range of approximately 600–900 nm. It is known that the shape of the absorption spectrum for Y6 is very sensitive to the film fabrication conditions, which is thought to be due to the difference in the local packing structure of Y6. − The almost identical shape for the Y6 absorption suggests that Y6 molecules are locally packed in a similar fashion in these blend films. It should be noted that PNBTz1 provided a sharp spectrum in which the 0–0 band was slightly stronger than the 0–1 band, whereas POTz1 exhibited a weaker 0–0 band relative to the 0–1 band, as both are similar to the case in the neat film.…”

Obvious improvement of dispersion of multiwall carbon nanotubes in polymer matrix through careful interface design

“…Now, we focus on the work function of POMA in the PAI composites. Firstly, the location of POMA in the PAI/MWCNTs/POMA ternary blend was investigated by calculating their surface energy levels, and the surface energies of these three materials were determined by measuring the contact angle of liquid droplets using Berthelot–Young's equation 53–55 . The mages of water droplet on PAI, POMA and MWCNTs films are shown in Figure 6.…”

“…Firstly, the location of POMA in the PAI/MWCNTs/POMA ternary blend was investigated by calculating their surface energy levels, and the surface energies of these three materials were determined by measuring the contact angle of liquid droplets using Berthelot-Young's equation. [53][54][55] The mages of water droplet on PAI, POMA and MWCNTs films are shown in Figure 6. The surface energy is evaluated to be 27.8 mJ m À1 for PAI, 20.4 mJ m À1 for POMA, and 10.9 mJ m À1 for MWCNTs, respectively.…”