Diketopyrrolopyrrole‐Based Conjugated Polymers Synthesized via Direct Arylation Polycondensation for High Mobility Pure n‐Channel Organic Field‐Effect Transistors

Abstract

High-performance unipolar n-type conjugated polymers (CPs) are critical for the development of organic electronics. In the current paper, four "weak donor-strong acceptor" n-type CPs based on pyridine flanked diketopyrrolopyrrole (PyDPP), namely PPyDPP1-4FBT, PPyDPP2-4FBT, PPyDPP1-4FTVT, and PPyDPP2-4FTVT, are synthesized via direct arylation polycondensation by using 3,3′,4,4′-tetrafluoro-2,2′-bithiophene (4FBT) or (E)-1,2-bis(3,4difluorothien-2-yl)ethene (4FTVT) as weak donor unit. All four polymers exhibit low-lying highest occupied molecular orbital (≈ −5.90 eV) and lowest unoccupied molecular orbital energy levels (≈ −3.70 eV). Top-gate/ bottom-contact organic field-effect transistors based on all four polymers display unipolar n-channel characteristics with electron mobility (µ e ) above 1 cm 2 V −1 s −1 in air, and presented linear |I SD | 1/2 −V GS plots and weak dependence of the extracted moblity on gate voltage (V GS ), indicative of the reliability of the extracted mobility values. Importantly, the devices based on PPyDPP1-4FBT and PPyDPP2-4FBT show a pure unipolar n-channel transistor behavior as revealed by the typical unipolar n-channel output characteristics and clear off-regimes in transfer characteristics. Attributed to its high crystallinity and favorable thin film morphology, PPyDPP2-4FBT shows the highest µ e of 2.45 cm 2 V −1 s −1 , which is among the highest for unipolar n-type CPs reported to date. This is also the first report for DPP based pure n-type CPs with µ e greater than 1 cm 2 V −1 s −1 .

Ambipolar Conjugated Polymers with Ultrahigh Balanced Hole and Electron Mobility for Printed Organic Complementary Logic via a Two‐Step CH Activation Strategy

“…This is owing to their highly lying lowest unoccupied molecular orbitals (LUMO), blockading efficient electron injection. Hence, on DPP's flanking and comonomer positions, electron acceptors are introduced to strengthen backbone electron‐deficiency. Meanwhile, resultant polymers' highest occupied molecular orbitals (HOMO) are also deepened to affect hole transport .…”

“…Hence, on DPP's flanking and comonomer positions, electron acceptors are introduced to strengthen backbone electron‐deficiency. Meanwhile, resultant polymers' highest occupied molecular orbitals (HOMO) are also deepened to affect hole transport . In general, very few DPP copolymers manage to demonstrate balanced hole and electron mobility simultaneously over 5 cm 2 V −1 s −1 , a benchmark quantifying copolymers for driving and logic utilities .…”

Indandione‐Terminated Quinoids: Facile Synthesis by Alkoxide‐Mediated Rearrangement Reaction and Semiconducting Properties

“…Top‐gate and bottom‐contact (TGBC) organic thin‐film transistors (OTFTs) were fabricated to investigate the semiconducting properties of these quinoids. No transistor characteristics were observed for the devices based on 5 a , 5 b , 5 d , or 5 g , whereas other compounds showed unipolar electron‐transport behavior as revealed by the clear off‐regimes in their transfer curves (Figure ; see Figures S19 and S20) . No hole injection and transport were observed for the devices of 5 c , 5 e , 5 f , 5 h , 5 i , 5 j , and 5 k although they showed relatively high‐lying HOMO levels (see Figure S21).…”

Direct arylation polymerization toward efficient synthesis of benzo[1,2‐c:4,5‐c'] dithiophene‐4,8‐dione based donor‐acceptor alternating copolymers for organic optoelectronic applications

“…π‐Conjugated polymers synthesized by direct arylation polymerization (DAP) have shown impressive performance in optoelectronics as well . For instance, Geng and cowrokers have used direct arylation to synthesize diketopyrrolopyrrole‐based copolymers containing fluorinated bithiophene derivatives in the conjugated backbones, which show ambipolar or unipolar n‐type high charge‐carrier mobilities in organic field effect transistors (OFETs). Recently, our group reported the direct arylation synthesis of a high performance polymer, poly[2,5‐bis((2‐hexyldecyl)oxy)phenylene)‐ alt ‐(5,6‐difluoro‐4,7‐di(thiophene‐2‐yl)benzo[c][1,2,5]thiadiazole) (denoted as PPDT2FBT), which gave PCEs up to 7.4% in organic BHJ solar cells .…”