Impact of Nonfullerene Acceptor Side Chain Variation on Transistor Mobility

Abstract

Organic photovoltaic power conversion efficiencies exceeding 14% can largely be attributed to the development of nonfullerene acceptors (NFAs). Many of these molecules are structural derivatives of IDTBR and ITIC, two common NFAs. By modifying the chemical structure of the acceptor, the optical absorption, energy levels, and bulk heterojunction morphology can be tuned. However, the effect of structural modifications on NFA charge transport properties has not yet been fully explored. In this work, the relationship between chemical structure, molecular packing, and charge transport, as measured in organic thin-film transistors (OTFTs), is investigated for two high performance NFAs, namely O-IDTBR and ITIC, along with their structural derivatives EH-IDTBR and ITIC-Th. O-IDTBR exhibits a higher n-type saturation field effect mobility of 0.12 cm 2 V −1 s −1 compared with the other acceptors investigated. This can be attributed to the linear side chains of O-IDTBR which direct an interdigitated columnar packing motif. The study provides insight into the transport properties and molecular packing of NFAs, thereby contributing to understanding the relationship between chemical structure, material properties, and device performance for these materials. The high electron mobility achieved by O-IDTBR also suggests its applications can be extended to use as an n-type semiconductor in OTFTs.

Nanostructure of organic semiconductor thin films: Molecular dynamics modeling with solvent evaporation

“…II A. Furthermore, MD simulations based on the experimentally obtained O-IDTBR and EH-IDTBR crystal structures [22] are presented to be able to compare the results from the thin-film simulations to corresponding results from perfectly ordered systems.…”

“…Recently, crystal structures based on x-ray diffraction measurements of single crystals grown by antisolvent vapor diffusion were published for O-IDTBR and EH-IDTBR [22]. As it has previously been shown that O-IDTBR has a crystallization transition at T c = 115 • C [20], a high structural order can potentially be induced locally in annealed thin-films of O-IDTBR, whereas this is not the case for EH-IDTBR (cf.…”

“…S1 for full names of all compounds mentioned in this paper] [19] have gained significant attention due to the stable, burn-in free, and highly efficient OPV devices based on these [8][9][10]15,20,21]. Furthermore, it has very recently been shown that the structural packing of IDTBR acceptors deduced from single crystals can explain the high n-type mobilities in organic thin-film transistors (OTFTs) of IDTBR derivatives [22]. Common for OPVs and OTFTs is that the active layer film thicknesses are often less than 100 nm, and with air-interface and substrate effects arguably becoming increasingly important with thinner films, it calls for inclusion of these in thin-film simulations [23].…”

European Academy of Sciences: 2020 Award Winners and New Members

“…McCulloch's research involves the design, synthesis and development of semiconducting small molecules and polymers for use as transistors for display, solar cells and most recently biological sensing. He was among the authors of a Communication in Angewandte Chemie on enhancing the lifetime of fullerene‐based solar cells, and in a Full Paper in Advanced Electronic Materials he described the impact of nonfullerene acceptor side‐chain variation on transistor mobility . McCulloch is a EurASC member since 2016.…”

Core Fluorination Enhances Solubility and Ambient Stability of an IDT‐Based n‐Type Semiconductor in Transistor Devices

“…[ 31,32 ] Several reports have also shown that these IDT‐based NFAs display promising performance in thin‐film transistor applications. [ 33,34 ] Alternative attempts have focused upon chemically modifying the core via the introduction of strong EWGs at the 4,9‐bridging positions of the IDT backbone (Figure 1b). Based on initial work by Zhao et al, Tian et al and more recently Peltier et al have investigated carbonyl bridge IDTs ( IDT‐di(O) ), for use in OFETs.…”