Semiconducting Polymers Based on Isoindigo and Its Derivatives: Synthetic Tactics, Structural Modifications, and Applications

Abstract

(1 of 33)benzothiadiazole (BT), [8,9] naphthalene diimide (NDI), [10,11] and isoindigo. [12][13][14] Isoindigo is an isomer of the wellknown industrial dye indigo and can be directly isolated from nature. [15,16] The structural difference between isoindigo and indigo is the relative positions of the nitrogen atom and the carbonyl group. In the indigo molecule, the nitrogen atoms are not connected to the carbonyl groups. Moreover, the nitrogen atoms in isoindigo molecule are connected with carbonyl groups. In 2012, indigo was reported as the active layer material of organic fieldeffect transistors (OFETs), which exhibited well-balanced ambipolar transport. [17] However, the H-bonded indigo showed extremely low solubility. For achieving good solution processibility, solubilizing side chains are introduced on the nitrogen atoms, which on the other hand break the intramolecular hydrogen bond, thereby reducing the molecular conjugation and limiting the electronics applications. [18] By contrast, the side chains on isoindigo do not break the hydrogen bond, and thus isoindigo is considered as a superior building block for organic electronic materials. [18,19] Since isoindigo was first used in organic electronics in 2010, [20] isoindigo-derived conjugated polymers have attracted considerable attention and have been developed rapidly due to the strong electron deficiency and high molecular planarity of isoindigo unit. [12,21] Moreover, compared with DPP, BT or NDI, isoindigo has a π-framework that can be readily modified. The structural feature of isoindigo endows itself many modification sites, including the side chains attached to the lactam nitrogen atoms, the center double bond, and the phenyl rings. More than twenty isoindigo derivatives have been reported. [22][23][24][25][26][27][28] Based on isoindigo and its derivatives, various isoindigo-derived conjugated polymers have been synthesized and many of them showed excellent performance. For example, using isoindigo-derived conjugated polymers, the hole and electron mobilities of p-and n-type OFETs have reached 14.4 and 14.9 cm 2 V −1 s −1 , respectively, and some ambipolar OFETs exhibited high hole/electron mobilities of up to 5.97/7.07 cm 2 V −1 s −1 . [29][30][31] The power conversion efficiencies (PCEs) of fullerene-containing organic photovoltaics (OPVs) and all-polymer solar cells (all-PSCs) based on isoindigo-derived polymers have exceeded 10% and 7%, respectively. [32,33] Furthermore, various structural modification

Cyclic and linear dithienyl-anthryl vinylenes: synthesis, X-ray crystallography, spectroscopic properties, and photoinduced mechanical motions

“…After drying in a vacuum, 5 was obtained as an orange solid (yield 0.0036 g, 3%) and 6 was obtained as an orange solid (yield 0.025 g, 12%). 1 H NMR of 5 (500 MHz, d-benzene): d 7.89 (q, J = 4.75 Hz, 8H, anthryl), 7.43 (q, J = 2.5 Hz, 8H, anthryl), 7.13 (s, 4H, 4-thienyl), 6 . GPC (polystyrene standards in THF): M n = 3500, PDI = M w / M n = 1.12.…”

“…Great attention has been paid to conjugated molecules due to their rigid structures and optical and electronic properties based on their delocalized p-systems, thus leading to the development of optoelectronic devices, such as organic lightemitting diodes (OLEDs), [1][2][3] organic photovoltaic devices, [4][5][6][7][8][9] organic field-effect transistors, 6,10,11 organic photorefractive devices, 12 and sensors. 3,[13][14][15] In particular, cyclic conjugated molecules are of significant interest because they have unique strained structures and features, affording organic nanogrids, 16,17 photonic crystals, 18 and highly efficient OLED devices.…”

Organic π‐Conjugated Molecules: From Nature to Artificial Applications. Where are the Boundaries?

“…IID molecule contains two lactam groups, where the nitrogen atoms are connected with carbonyl groups and can participate in forming fully conjugated molecules [59] . In addition, IID derivatives show comprehensive structural modularity and significantly higher solubility in common organic solvents than ID, which facilitates its applicability and makes IID a superior building block for materials in organic electronics [60] . The IID‐based derivative was first used as an organic semiconductor in 2010 at BHJ‐OSC, [61] and since then until now, this group of materials has seen tremendous developments in both OPV and OFET devices and is still pushing the performance boundaries further [60] …”

Towards modulating the colour hues of isoindigo-based electrochromic polymers through variation of thiophene-based donor groups

“…Isoindigo is a structural isomer of the well-known indigo dye. Since its debut in 2009 as a promising building block for organic photovoltaics (PV) by Reynolds' group, 36,37 isoindigo has emerged as a popular choice of acceptor group in the construction of donor-acceptor type conjugated polymers for optoelectronic applications, [38][39][40][41] namely organic field effect transistors (FETs) and PVs. Owing to its high electron-withdrawing nature, conjugated co-polymers with a low E g value can be achieved.…”