Significant Improvement of Semiconducting Performance of the Diketopyrrolopyrrole–Quaterthiophene Conjugated Polymer through Side-Chain Engineering via Hydrogen-Bonding

Abstract

Three diketopyrrolopyrrole (DPP)-quaterthiophene conjugated polymers, pDPP4T-1, pDPP4T-2, and pDPP4T-3, in which the molar ratios of the urea-containing alkyl chains vs branching alkyl chains are 1:30, 1:20, and 1:10, respectively, were prepared and investigated. In comparison with pDPP4T without urea groups in the alkyl side chains and pDPP4T-A, pDPP4T-B, and pDPP4T-C containing both linear and branched alkyl chains, thin films of pDPP4T-1, pDPP4T-2, and pDPP4T-3 exhibit higher hole mobilities; thin-film mobility increases in the order pDPP4T-1 < pDPP4T-2 < pDPP4T-3, and hole mobility of a thin film of pDPP4T-3 can reach 13.1 cm(2) V(-1) s(-1) after thermal annealing at just 100 °C. The incorporation of urea groups in the alkyl side chains also has an interesting effect on the photovoltaic performances of DPP-quaterthiophene conjugated polymers after blending with PC71BM. Blended thin films of pDPP4T-1:PC71BM, pDPP4T-2:PC71BM, and pDPP4T-3:PC71BM exhibit higher power conversion efficiencies (PCEs) than pDPP4T:PC71BM, pDPP4T-A:PC71BM, pDPP4T-B:PC71BM, and pDPP4T-C:PC71BM. The PCE of pDPP4T-1:PC71BM reaches 6.8%. Thin films of pDPP4T-1, pDPP4T-2, and pDPP4T-3 and corresponding thin films with PC71BM were characterized with AFM, GIXRD, and STEM. The results reveal that the lamellar packing order of the alkyl chains is obviously enhanced for thin films of pDPP4T-1, pDPP4T-2, and pDPP4T-3; after thermal annealing, slight inter-chain π-π stacking emerges for pDPP4T-2 and pDPP4T-3. Blends of pDPP4T-1, pDPP4T-2, and pDPP4T-3 with PC71BM show a more pronounced micro-phase separation. These observations suggest that the presence of urea groups may further facilitate the assemblies of these conjugated polymers into nanofibers and ordered aggregation of PC71BM.

High‐Mobility Naphthalene Diimide and Selenophene‐Vinylene‐Selenophene‐Based Conjugated Polymer: n‐Channel Organic Field‐Effect Transistors and Structure–Property Relationship

“…[1][2][3][4][5][6][7] Such progress coupled with the high compatibility of solution-processable organic semiconductors with plastic or metal foil substrates makes them ideal candidates for cost-effective, mechanically flexible electronic devices for various applications, such as printed radio frequency identification tags for item-level tagging, drivers for flexible displays, wearable electronics, distributed sensors, and integrated, nonvolatile memory devices. [8][9][10][11][12][13][14][15][16][17][18][19][20] [21][22][23][24][25] Such remarkable p-channel mobilities, obtained in devices with fairly promising shelf-life and operational stabilities, have been demonstrated with conjugated polymers based on new building units, such as diketopyrrolopyrrole, [24,26,27] isoindigo, [28,29] and indacenodithiophene. [30] Similar efforts have been devoted to improving n-channel polymer semiconductors, with the performances of n-type devices still lagging behind their p-channel counterparts.…”

Injection Length in Staggered Organic Thin Film Transistors: Assessment and Implications for Device Downscaling

“…[2][3][4][5][6][7][8][9][10][11][12] Therefore by scaling the channel length down to 10-1 μm, in principle OTFTs should be able to operate at relatively high (1-10 MHz) frequencies at reasonable (<10 V) applied voltages. [ 13 ] In practice, apart from some reports, [13][14][15][16][17][18][19][20][21][22] this is often not easy to achieve because of injection issues: [ 23,24 ] contact resistances tend to become dominant over the channel resistance in short channel transistors reducing the expected improvement of device performances.…”

Difluorobenzothiadiazole based two-dimensional conjugated polymers with triphenylamine substituted moieties as pendants for bulk heterojunction solar cells

“…Major advances in the solar energy conversion efficiencies of PSCs have been accomplished by replacing the double-layer cell with a bulk-heterojunction (BHJ) based on a conjugated polymer/fullerene derivative blend as the photoactive layer [8][9][10]. The bipolar characteristics of D/A-type conjugated polymers, containing both electron-and hole-transporting moieties, can result in lower-energy band gaps and higher charge mobilities for the photoactive layers, thereby enhancing the PV efficiencies of PSCs [11][12][13][14][15]. Polythiophene (PT) derivatives bearing electron-donating and -withdrawing pendant groups, so-called two-dimensional (2-D) low band gap conjugated polymers, have been proposed by several groups for PSC applications [16][17][18][19][20][21][22][23][24][25].…”