Addition of the Lewis Acid Zn(C₆F₅)₂ Enables Organic Transistors with a Maximum Hole Mobility in Excess of 20 cm² V⁻¹ s⁻¹

Abstract

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.201900871.Incorporating the molecular organic Lewis acid tris(pentafluorophenyl)borane [B(C 6 F 5 ) 3 ] into organic semiconductors has shown remarkable promise in recent years for controlling the operating characteristics and performance of various opto/electronic devices, including, light-emitting diodes, solar cells, and organic thin-film transistors (OTFTs). Despite the demonstrated potential, however, to date most of the work has been limited to B(C 6 F 5 ) 3 with the latter serving as the prototypical air-stable molecular Lewis acid system. Herein, the use of bis(pentafluorophenyl)zinc [Zn(C 6 F 5 ) 2 ] is reported as an alternative Lewis acid additive in high-hole-mobility OTFTs based on small-molecule:polymer blends comprising 2,7-dioctyl[1]benzothieno [3,2-b][1]benzothiophene and indacenodithiophene-benzothiadiazole. Systematic analysis of the materials and device characteristics supports the hypothesis that Zn(C 6 F 5 ) 2 acts simultaneously as a p-dopant and a microstructure modifier.It is proposed that it is the combination of these synergistic effects that leads to OTFTs with a maximum hole mobility value of 21.5 cm 2 V −1 s −1 . The work not only highlights Zn(C 6 F 5 ) 2 as a promising new additive for next-generation optoelectronic devices, but also opens up new avenues in the search for high-mobility organic semiconductors.

17.1% Efficient Single‐Junction Organic Solar Cells Enabled by n‐Type Doping of the Bulk‐Heterojunction

“…The intentional introduction of molecular dopants has been used extensively to alter the charge transport properties of organic semiconductors, particularly in the area of organic thin‐film transistors (OTFTs) for which some of the highest carrier mobilities have been achieved via this method 6–9. Molecular doping relies on charge transfer interaction(s) between the dopant and the host semiconductor, which ultimately results in formation of free carriers 10,11.…”

“…Molecular doping relies on charge transfer interaction(s) between the dopant and the host semiconductor, which ultimately results in formation of free carriers 10,11. Recent studies have shown that molecular doping may, under certain conditions, induce multiple synergistic effects including microstructural changes to the host semiconductor and drastic improvement in charge carrier transport 6,8,9. These effects were shown to be the result of the dual functionality of the molecular dopants, acting both as electronic dopants and microstructure modifying agents.…”

“…These effects were shown to be the result of the dual functionality of the molecular dopants, acting both as electronic dopants and microstructure modifying agents. Noticeable dopant‐induced effects included enhanced layer crystallinity and reduced trap density due to increased free carrier concentration 8,9…”

Doping High‐Mobility Donor–Acceptor Copolymer Semiconductors with an Organic Salt for High‐Performance Thermoelectric Materials

“…To further confirm that PCDTPT was doped by TrTPFB, electron spin resonance (ESR) measurements were performed at room temperature. As seen in Figure 2b, even the 1 wt% TrTPFB doped sample shows strong paramagnetic signals, demonstrating the existence of unpaired electrons 34. In contrast, PCDTPT and pure TrTPFB (see Figure S2a, Supporting Information) samples were observed without paramagnetic signals.…”

“…These dopants either have a very deep lowest unoccupied molecule orbitals (LUMO) (p‐dopants) or a very shallow highest occupied molecule orbitals (HOMO) (n‐dopants), and can effectively dope the semiconductors by forming ion‐pairs or charge transfer complex 32. In the past few years, the dopants and doping techniques for organic semiconductors have been progressed tremendously, with novel dopants like Lewis acid (for p‐doing) and Lewis base (for n‐doping) demonstrating significant doping effects for improving performance in OFETs or OPVs 33–36. However, these new doping techniques have not been fully implemented for OTE applications, and therefore it is worth exploring novel dopants to further enhance the thermoelectric performance of OTEs.…”