Perylene Diimide-Fused Dithiophenepyrroles with Different End Groups as Acceptors for Organic Photovoltaics

Abstract

In this study, we synthesized four new A–DA′D–A acceptors (where A and D represent acceptor and donor chemical units) incorporating perylene diimide units (A′) as their core structures and presenting various modes of halogenation and substitution of the functional groups at their end groups (A). In these acceptors, by fusing dithiophenepyrrole (DTP) moieties (D) to the helical perylene diimide dimer (hPDI) to form fused-hPDI (FhPDI) cores, we could increase the D/A′ oscillator strength in the cores and, thus, the intensity of intramolecular charge transfer (ICT), thereby enhancing the intensity of the absorption bands. With four different end group unitsIC2F, IC2Cl, IO2F, and IO2Cltested, each of these acceptor molecules exhibited different optical characteristics. Among all of these systems, the organic photovoltaic device incorporating the polymer PCE10 blended with the acceptor FhPDI-IC2F (1:1.1 wt %) had the highest power conversion efficiency (PCE) of 9.0%; the optimal PCEs of PCE10:FhPDI-IO2F, PCE10:FhPDI-IO2Cl, and PCE10:FhPDI-IC2Cl (1:1.1 wt %) devices were 5.2, 4.7, and 7.7%, respectively. The relatively high PCE of the PCE10:FhPDI-IC2F device resulted primarily from the higher absorption coefficients of the FhPDI-IC2F acceptor, lower energy loss, and more efficient charge transfer; the FhPDI-IC2F system experienced a lower degree of geminate recombinationas a result of improved delocalization of π-electrons along the acceptor unitrelative to that of the other three acceptors systems. Thus, altering the end groups of multichromophoric PDI units can increase the PCEs of devices incorporating PDI-derived materials and might also be a new pathway for the creation of other valuable fused-ring derivatives.

High-Efficiency Semitransparent Organic Photovoltaics Containing Vertical Multiheterojunctions

“…The SD trilayer devices exhibited a prolonged T 80 lifetime of 495 s, outperforming both the BHJ ( T 80 = 280 s) and SD bilayer ( T 80 = 457 s) devices. This preliminary result suggests that our SD trilayer strategy not only benefited the device performance, with tunability of the vertical phase distribution and charge transportation pathways, but also improved the device stability under damp-heat conditions . The SD trilayer strategy provides tunable vertical phase distribution and two interfacial structures of D18 with Y1 and Y1 with Y6, as compared to one interfacial structure in the case of bilayer (D18 with Y6), where the well-mixed donor and acceptors are present in the interfacial structure and thus can prevent water molecule permeation and penetration in the active layer, retaining the active layer morphology more effectively and thus benefiting the device stability under double 85 conditions.…”

“…This preliminary result suggests that our SD trilayer strategy not only benefited the device performance, with tunability of the vertical phase distribution and charge transportation pathways, but also improved the device stability under damp-heat conditions. 49 The SD trilayer strategy provides tunable vertical phase distribution and two interfacial structures of D18 with Y1 and Y1 with Y6, as compared to one interfacial structure in the case of bilayer (D18 with Y6), where the well-mixed donor and acceptors are present in the interfacial structure and thus can prevent water molecule permeation and penetration in the active layer, retaining the active layer morphology more effectively and thus benefiting the device stability under double 85 conditions. Moreover, our SD trilayer devices contained two interfacial structures that can prevent the migration of molecules under heating, as compared to the bilayer and BHJ cases, thus achieving improved thermal stability.…”

Perylene Diimide‐based Non‐fullerene Acceptors With A‐D‐A′‐D‐A Architecture For Organic Solar Cells

“…Besides core units, the terminal groups also have a remarkable impact on performances of NFAs. [44][45][46][47] For instance, when the fluorine (F) atom was introduced into the end-groups, the significant improved PCEs of the fused-ring electron acceptors (FREAs) were achieved. This can be ascribed to that the introduction of F atoms facilitate the intramolecular and intermolecular interaction, resulting in enhancing short-circuit current density (J SC ) and fill factor (FF).…”

“…These results also demonstrated that the type of D‐A’‐D core could affect the photovoltaic performance. Besides core units, the terminal groups also have a remarkable impact on performances of NFAs [44–47] . For instance, when the fluorine (F) atom was introduced into the end‐groups, the significant improved PCEs of the fused‐ring electron acceptors (FREAs) were achieved.…”

Binary alloy of functionalized small-molecule acceptors with the A–DA′D–A structure for ternary-blend photovoltaics displaying high open-circuit voltages and efficiencies

“…Several molecular engineering methods have been developed as design strategies toward preparing suitable core units, side chains, and end groups. These methods involve: (i) fine-tuning suitable energy levels through the insertion of heteroatoms or the attachment of functional groups, 11 (ii) extending the core conjugated structure through backbone modification, 12 and (iii) side-chain engineering to provide moderate solubility and thereby suitable aggregation properties 13 and preferred aggregated orientations. 14 These structural variations can affect the photoelectronic properties of the materials as well as their aggregation in blends and thus, the morphologies of their active layers.…”