Record‐High Electron Mobility Exceeding 16 cm² V⁻¹ s⁻¹ in Bisisoindigo‐Based Polymer Semiconductor with a Fully Locked Conjugated Backbone

Abstract

and technologies in improving their charge-transport properties have been explored and practiced from molecular design, [9,10] synthetic method, [11,12] purification, [13,14] thin film microstructural optimization, [15,16] device configuration and fabrication, [17−20] to device interface engineering. [21−23] To be blunt, however, the carrier mobilities and device stability of polymer semiconductors nowadays are generally not adequate for the requirements of next-generation organic electronics. For example, the polymer semiconductors with carrier mobilities greater than 10 cm 2 V −1 s −1 are still few so far and almost all of them are thiophene-flanked diketopyrrolopyrrolebased copolymers (Table S1, Supporting Information). More importantly, the ambipolar or n-type polymer semiconductors with electron mobility exceeding 10 cm 2 V −1 s −1 are quite rare, although they are of great importance for fabricating polymer field-effect transistors (PFETs) and complementary metal-oxidesemiconductor-like circuits toward commercial high-grade electronics. [17,24−27] Nevertheless, the obtained fundamental understandings on charge-carrier transport mechanism in the exploring process still shows us invaluable guidelines for constructing high-mobility polymer semiconductors and PFETs. One fundamental understanding is "intrachain charge-carrier transport along the conjugated backbone chains is much faster than interchain charge-carrier transport, and the key limitation Polymer semiconductors with mobilities exceeding 10 cm 2 V −1 s −1 , especially ambipolar and n-type polymer semiconductors, are still rare, although they are of great importance for fabricating polymer field-effect transistors (PFETs) toward commercial high-grade electronics. Herein, two novel donor−acceptor copolymers, PNFFN-DTE and PNFFN-FDTE, are designed and synthesized based on the electron-deficient bisisoindigo (NFFN) and electron-rich dithienylethylenes (DTE or FDTE). The copolymer PNFFN-DTE, containing NFFN and DTE, possesses a partially locked polymeric conjugated backbone, whereas PNFFN-FDTE, containing NFFN and FDTE, has a fully locked one. Fluorine atoms in FDTE not only induce the formation of additional CH•••F hydrogen bonds, but also lower frontier molecular orbitals for PNFFN-FDTE. Both PNFFN-DTE and PNFFN-FDTE form more ordered molecular packing in thin films prepared from a polymer solution in bicomponent solvent containing 1,2-dichlorobenzene (DCB) and 1-chloronaphthalene (with volume ratio of 99.2/0.8) than pure DCB. The two copolymers-based flexible PFETs exhibit ambipolar charge-transport properties. Notably, the bicomponent solvent-processed PNFFN-FDTE-based PFETs afford a high electron mobility of 16.67 cm 2 V −1 s −1 , which is the highest electron-transport mobility for PFETs reported so far. The high electron mobility of PNFFN-FDTE is attributed to its fully locked conjugated backbone, dense molecular packing, and much matched LUMO energy level.

Ambipolar Charge Transport in p-Type Cyclopentadithiophene-Based Polymer Semiconductors Enabled by D–A–A–D Configuration

“…The P1 thin film also exhibited face-on crystallites with a weak (010) diffraction peak in the OOP direction. The mixed edge-on/face-on crystalline structure observed for P1 is known to improve the charge transport of electrons and holes via the 3D percolation of polymer crystallites. ,,− Hence, P1 is expected to have improved electron and hole mobilities compared with P2 and PCDTPT.…”

“…Organic field-effect transistors (OFETs) based on donor–acceptor (D–A)-type polymer semiconductors have attracted increasing attention owing to a remarkably enhanced charge carrier mobility (μ) (>1 cm 2 V –1 s –1 ). − In addition to improving the charge carrier mobility, the alternating D–A structure of polymer semiconductors enables an ambipolar charge transport by adjusting the energy levels to be favorable for the efficient injection of electron and hole charge carriers from adjacent source and/or drain electrodes. − Although OFETs based on ambipolar polymer semiconductors require high driving power due to their high off-current, , the ambipolar charge transport in a single-component polymer semiconductor thin film provides the advantage of the facile fabrication of ambipolar OFETs and logic circuits, including complementary metal-oxide semiconductor (CMOS) inverters. − Hence, researchers have developed various D–A-type ambipolar polymer semiconductors and investigated their charge transport characteristics. − However, identifying the ideal D–A configuration among numerous D and A moieties for high electron and hole mobilities with hysteresis-free transistor characteristics requires considerable effort and possibly involves several rounds of trial and error. Therefore, despite the reasonably deepened conduction band edge (CBE) energy levels of D–A-type polymer semiconductors, the electron transport in D–A-type polymer semiconductors is often limited …”

Magnetoresistance in Organic Spin Valves Based on Acid‐Exfoliated 2D Covalent Organic Frameworks Thin Films

“…Owing to the insolubility of the extended 2D π-conjugated skeleton in common organic solvents, conventional organic solution processing means such as spin coating and drop casting for small molecules or 1D polymers are incompatible with this situation. [62,63] Therefore, a scalable chemical exfoliation approach utilizing temporarily protonated imine linkages was employed to prepare free-standing 2D COF films on water surfaces, [54] which could be transferred to arbitrary substrate including FM electrodes (Figure 2). In the preparation process of the COF films, the Py-Np COF powder was first dispersed into a mixture of trifluoroacetic acid (TFA) and water (v : v = 20 : 1), in which a small amount of water would facilitate the dissolution of COF powder.…”

Aggregation behaviour of pyrene-based luminescent materials, from molecular design and optical properties to application

“…Some of these compounds show high electron mobilities as high as 16 cm 2 V −1 s −1 . 236 Thus, researchers have devoted time to functionalizing the pyrene to form electron-deficient units by employing molecular design strategies. Pei et al 237 first synthesized a new pyrene-based diimide 128 from 1,6-dibromopyrene 125 by the following synthetic route (Fig.…”