Thin film morphology and charge carrier mobility of diketopyrrolopyrrole based conjugated polymers

Abstract

18 A series of narrow bandgap donor-acceptor (D-A) type π-conjugated polymers consisting of 19 thiophene (Th)-or furan (Fu)-flanked diketopyrrolopyrroles (DPPs) as acceptor units and 20 thieno[3,2-b]thiophene (TT) or didodecyloxybenzo[1,2-b;3,4-b]dithiophene (BDT) moieties as 21 donor units were synthesized. Cyclic voltammetry and UV-vis absorption studies revealed that 22 both the heteroatom substitution in the aromatic end-groups of DPPs and variations in the 23 chemical backbone influenced the bandgap of these polymers. The TT-based polymers showed a 24 better thermal stability than their BDT analogues. P(ThDPP-TT) with better backbone planarity 25 among the polymers being studied was found to organize in edge-on fashion on silicon/silicon 26 dioxide surface, while all others showed a mixed type of both face-and edge-on arrangements. A 27 substantial reduction in the thin film order and packing of the polymer chains was observed as 28 the terminal thiophene units of DPP were replaced with furan. However, the furyl substituted 29 polymer exhibited relatively high charge carrier mobility possibly due to improved conduction 30 along the polymer backbone. The charge carrier transport properties of these polymers in organic 31 M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 2 field effect transistors (OFETs) were found to be influenced by incorporated donor units. 1Polymers with BDT-donor group exhibited unipolar hole transport, while those with TT units 2 were ambipolar in nature. The present study demonstrates a systematic investigation of the 3 structure-property relationships of D-A type DPP based π-conjugated copolymers which may 4 enlighten better design strategy of polymers with novel chemical structures in the future. 5Keywords: diketopyrrolopyrole; heteroatom substitution; organic field effect transistors; thin 6 film morphology; charge carrier mobility; ambipolar polymer. 7 8 9

Diketopyrrolopyrrole-based conjugated polymers synthesized by direct arylation polycondensation for anisole-processed high mobility organic thin-film transistors

“…Fu-F and Fu-Cl display deeper HOMO levels than Th-F and Th-Cl , which had the E HOMO values of −5.34 and −5.41 eV, respectively, owing to the high ionization potential of furan. 69…”

Toward High Mobility Green Solvent‐Processable Conjugated Polymers: A Systematic Study on Chalcogen Effect in Poly(Diketopyrrolopyrrole‐alt‐Terchalcogenophene)s

“…Film cyclic voltammograms of the polymers (Figure S4, Supporting Information) were conducted to estimate the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels, which were in the range of −5.22 to −5.20 and −3.32 to −3.25 eV for FDPP‐based polymers, −5.20 to −5.10 and −3.28 to −3.20 eV for TDPP‐based polymers, −5.05 to −5.04 and −3.36 to −3.32 eV for SeDPP‐based polymers. The FDPP‐based polymers exhibited the relatively deep HOMO energy levels due to the high ionization potential of furan, [ 60 ] while the SeDPP‐based polymers showed the relatively shallow HOMO and deep LUMO energy levels. The replacement of O or S atoms by Se in chalcogenophene‐flanked DPP increases the electron donating ability, narrows the band gap, and lowers the oxidation potential.…”

“…However, the contradictory results were also obtained, and some furan-and selenophene-containing DPPbased CPs exhibited unexpected low OTFT performance owing to poor film morphology and low film order. [57][58][59][60] We postulate that the type and position of chalcogenophenes relative to DPP unit are crucial to the property of the resulting CPs. Therefore, in order to obtain high mobility CPs processable with ecofriendly solvents, insights into the structure-property correlation to understand chalcogen effect on the semiconducting property and solubility of DPP-based CPs are highly desired.…”