Crystal structures in state-of-the-art non-fullerene electron acceptors

Abstract

Great progress in power conversion efficiencies (PCEs) of the organic photovoltaics (OPVs) has been made by employing non-fullerene acceptors (NFAs). In order to further promote the device performance, it is...

Electron Transport in Organic Photovoltaic Acceptor Materials: Improving the Carrier Mobilities by Intramolecular and Intermolecular Modulations

“…It should be noted that the packing patterns in the crystal can be observed in the film . We thus highlight that the state-of-the-art SMAs should possess the capability to form robust 3D π–π stacking networks. , This is beneficial to achieving efficient electron transport and high FFs.…”

“…The first ITIC crystal structure was reported in 2017, which exhibits a 1D edge-to-face stacking without π–π interactions . Since then, hundreds of crystals for both ITIC-type and Y6-type acceptors were grown. ,− Nevertheless, the end-group π–π stacking can be found in most of them. Even for ITIC, another three polymorphs of 1D, 2D, or 3D π–π stacking exist .…”

“…47 We thus highlight that the state-of-the-art SMAs should possess the capability to form robust 3D π−π stacking networks. 43,49 This is beneficial to achieving efficient electron transport and high FFs.…”

Understanding the role of non-fullerene acceptor crystallinity in the charge transport properties and performance of organic solar cells

“…A growing variety of NFA single-crystals are now being reported, 8,14,15,[19][20][21][22][23][24][25][26][27][28][29][30][31][32] from which useful information on the molecular packing can be derived. Still, bridging the molecular scale from molecular packing in single-crystals to the one found in Bulk Heterojunctions (BHJs) needs more detailed investigations.…”

“…Still, bridging the molecular scale from molecular packing in single-crystals to the one found in Bulk Heterojunctions (BHJs) needs more detailed investigations. 10,32,33 The identication of the packing motif of the NFA within a donor:acceptor blend is a challenging task, yet the structural analysis is commonly based on Grazing Incidence Wide Angle Xray Scattering (GIWAXS) patterns that lack enough diffraction features for the structural determination. The analysis of the main Bragg peaks of the NFA, oen referred to as the lamellar (100) and the p-p stacking (010) distances, [34][35][36] is routinely considered enough to draw conclusions.…”