A Novel Alkylated Indacenodithieno[3,2‐b]thiophene‐Based Polymer for High‐Performance Field‐Effect Transistors

Abstract

A novel rigid donor monomer, indacenodithieno[3,2‐b]thiophene (IDTT), containing linear alkyl chains, is reported. Its copolymer with benzothiadiazole is an excellent p‐type semiconductor, affording a mobility of 6.6 cm2 V−1 s−1 in top‐gated field‐effect transistors with pentafluorobenzenethiol‐modified Au electrodes. Electrode treatment with solution‐deposited copper(I) thiocyanate (CuSCN) has a beneficial hole‐injection/electron‐blocking effect, further enhancing the mobility to 8.7 cm2 V−1 s−1.

An Alkylated Indacenodithieno[3,2‐b]thiophene‐Based Nonfullerene Acceptor with High Crystallinity Exhibiting Single Junction Solar Cell Efficiencies Greater than 13% with Low Voltage Losses

“…Although simple conceptually, the synthesis of IDTT with alkyl side chains is challenging since the corresponding trialkyl cations tend to rearrange or eliminate under analogous Friedel-Crafts-type ring closing reactions. [23] Herein, we report a novel route to prepare an alkylated IDTT-…”

“…The advantage of this route to alkylated IDTT is that all intermediates are soluble and readily purified, in contrast to our previous route in which several intermediates were insoluble and hence difficult to purify and characterize. [23] The ester groups on 3 were readily converted to aldehyde groups via a two-step reduction/oxidation route using LiAlH 4 , followed by the Dess-Martin periodinate to afford IDTT-dialdehyde 5 in 76% yield over two steps. The final acceptor C8-ITIC was prepared by the Knoevenagel condensation reaction of 5 and IC in a yield of 82%.…”

Naphthacenodithiophene Based Polymers—New Members of the Acenodithiophene Family Exhibiting High Mobility and Power Conversion Efficiency

“…[17] Additionally, the slightly higher Urbach energy as well as the increased sub-bandgap absorption between 1.0 and 1.6 eV of the high molecular weight fraction of C 16 -NDT-BT indicate that disorder in this polymer sample is increased, perhaps due to the higher viscosity of the longer chains, impeding cooperative motion required for long range organization. [27] Nevertheless, overall it seems surprising that by extending the IDT-conjugated backbone into a more rigid NDT unit, the energetic disorder in NDT-BT is increased by at least 9 meV as compared to IDT-BT.…”

“…This could also explain, why in NDT-BT, there is no significant change between the n-hexadecyl and 2-ethylhexyl side chains, whereas for IDT-BT, a drop in charge carrier mobility and an increase in disorder can be observed. [17] …”

“…[15][16][17][18] The high mobility in IDT copolymers is currently understood to be a consequence of backbone co-planarity and rigidity, resulting in a low energetic disorder, leading to charge transport taking place mainly along the polymer backbone and a limited amount of charge hopping between chains. [14][15][16][17] In addition to this backbone rigidity, alkyl chains can be easily attached and varied, having both a profound effect on performance, but also dramatically increasing solubility, thus facilitating dissolution in nonchlorinated solvents. [19] Although the transport properties of this polymer class are outstanding, solar cell device performance has remained modest, with less than 7% PCE achieved.…”