Porphyrin Acceptors Improve the Crystallization of Y6 and the Exciton Dissociation in Ternary Organic Solar Cells

Abstract

The development of the third component is very important for ternary organic solar cells (OSCs). Herein, we synthesized two porphyrin electron acceptors (Zn-Por-IC4F and Zn-Por-IC) with an A-2π-D-2π-A (A: electron acceptor unit, D: electron donor unit) structure as the third component for PTB7-Th:Y6 devices. Zn-Por-IC4F and Zn-Por-IC in the ternary OSCs can improve the crystallization of Y6 and the exciton dissociation, therefore enhancing their fill factors (FF). As a result, the power conversion efficiencies (PCEs) of the PTB7-Th:Y6:Zn-Por-IC4F and PTB7-Th:Y6:Zn-Por-IC ternary OSCs are improved to 11.6 and 10.67%, which are increased by 21 and 11.5%, respectively, compared with that of PTB7-Th:Y6 binary devices with a PCE of 9.57%. This is the first report that porphyrins are employed as electron acceptors in ternary OSCs, though porphyrins have been widely used as donor materials of OSCs, which may open up an avenue for the applications of porphyrins in OSCs and provide guidelines for designing photovoltaic materials.

Novel Beta-Functionalized Porphyrins Approaching 11% Efficiency for Organic Solar Cells

“…The surface morphologies of the blend films were investigated by atomic force microscopy (AFM). As shown in Figure , the DIO + TA + SVA-treated films showed enlarged surface root-mean-square (RMS) roughness compared with the as-cast films, which may be ascribed to the fact that the postprocessing treatments promoted the recrystallization of the molecules to form donor-enriched and acceptor-enriched regions, which was beneficial for the exciton dissociation and charge transport in the OSCs.…”

Fine-tuning of film morphology through addition of a third component enables organic solar cells with efficiency over 18%

“…Often, the third component plays a crucial role in the intercharge transport mechanism, the morphology modulation of the active layer, stability, and the distribution of the vertical gradient of the acceptor within the active layer. 13,[30][31][32][33][34] PCE of the devices can be significantly enhanced by the addition of a third component, with the optimization of ternary blend film morphology being a crucial aspect. 35,36 Various strategies for morphological optimization exist, including thermal annealing, additives, conjugated backbone modulation, and end group halogenation etc.…”

“…Often, the third component plays a crucial role in the inter-charge transport mechanism, the morphology modulation of the active layer, stability, and the distribution of the vertical gradient of the acceptor within the active layer. 13,30–34…”