Electron Mobility of Diketopyrrolopyrrole Copolymers Is Robust against Homocoupling Defects

Abstract

Structural defects in semiconducting conjugated polymers are usually suspected to deteriorate their properties and device performance and therefore complicate batch-to-batch reproducibility. This study investigates homocoupling (hc) defects in copolymers made from dithiazolyldiketopyrrolopyrrole (TzDPPTz) and tetrafluorobenzene (F4) by direct arylation polycondensation (DAP). Hc defects are quantified by 1 H NMR spectroscopy with good accuracy, and the effect of several reaction parameters on the TzDPPTz hc content in the resulting copolymers PTzDPPTzF4 is investigated in detail. A range of polymers with hc contents between 0.6 and 12.4% is used for a detailed structure− function relationship study. Experimentally, it is observed that TzDPPTz hc defects cause bathochromically shifted absorption spectra, decrease photoluminescence, and lower the lowest unoccupied molecular orbital (LUMO) energy level. Thin film morphology, nanostructure, and electron mobility probed by field-effect devices is marginally or not affected. The latter result is explained by theoretical calculations that suggest a localization of the highest occupied molecular orbital on the hc defect, but not that of the LUMO, the latter being relevant for electron transport. Thus, under these conditions, the hc content is not limiting device performance, which makes PTzDPPTzF4 a robust electron-transporting copolymer. These results are promising in the context of batch-to-batch reproducibility and further guide efforts toward a more detailed understanding of hc−function relationships.

Efficient room temperature catalytic synthesis of alternating conjugated copolymers via C-S bond activation

“…This direct comparison underscores the attraction of lower temperature cross-coupling polymerization via C-S cleavage. Although several studies argue that the charge transport mobilities of copolymer is robust against homocoupling structural defects in the OFETs, a deep understanding and interpretation from the trap densities perspective is necessary 36 , 37 . Here, thermal admittance spectroscopy (TAS) analysis 38 was used to quantize the reduction of trap states in P2-CS and P2-CI films, respectively.…”

Hydrogen Bonds Control Single-Chain Conformation, Crystallinity, and Electron Transport in Isoelectronic Diketopyrrolopyrrole Copolymers

“…DAP is an economically attractive method that allows for the elimination of toxic stannanes required for the Stille polycondensations (Scheme ). , The synthetic procedures of these two polymers and their corresponding monomers ThDPPTh and TzDPPTz are described in the Supporting Information. , Due to different C–H reactivities of the monomers ThDPPTh and TzDPPTz, also different experimental parameters were required to obtain PThDPPThF4 and PTzDPPTzF4 with similar MWs and homocoupling (hc) contents. The MWs were determined by size exclusion chromatography (SEC) to yield similar M n,SEC values of 12.3 and 11.3 kg mol –1 for PThDPPThF4 and PTzDPPTzF4, respectively (Table , Figure S1).…”

“…Conjugated polymers based on diketopyrrolopyrrole (DPP) have seen a steep rise in scientific interest and OFET performance during the last decade due to their high structural planarity and simple synthetic access. − Recently, high-performance n-type copolymers based on DPP have also received increased attention as the electron-deficient nature of the DPP core itself can be further modulated by the flanking units and comonomers. ,,− Thus, the n-type or ambipolar performance of DPP-based copolymers in OFET devices is largely tunable depending on the nature of the DPP core as well as of the comonomer. , Previously, we reported the excellent electron mobilities and transport behavior of the DPP-based copolymer PThDPPThF4 (Scheme ), with electron mobilities up to 3 cm 2 V –1 s –1 being achieved. , By copolymerizing the simple and widely used building block dithienyldiketopyrrolopyrrole (ThDPPTh) with the electron-deficient comonomer 1,4-dibromo-2,3,5,6-tetrafluorobenzene (F4Br 2 ) via direct arylation polycondensation (DAP), the resulting copolymer PThDPPThF4 exhibited a predominant n-type performance. Based on this straightforward synthetic scheme and these promising results, we were interested in the impact of further derivatization of PThDPPThF4, for example, by further lowering its LUMO energy level when replacing thiophene (Th) by thiazole (Tz) . Conjugated polymers with thiazole units show promising results with their regiochemistry, opening up many possibilities both in terms of synthetic access as well as structural diversity. ,,− …”

Deciphering Photoinduced Charge Transfer Dynamics in a Cross-Linked Graphene–Dye Nanohybrid

“… 30 , 32 The oligomer may be broken into subunits via twisting between TDPP units 51 or homocoupling defect sites. 53 , 54 Within 1.5 ps, these states may decay due to energy transfer either to EXG or to the TDPP-EXG covalent bond site; we are unable to determine whether this process takes place in parallel or sequentially with the 18 ps process. We also do not rule out the possibility that an SE band overlaps with the positive features for the 1.5 ps DAS; indeed, the measured steady-state PL ( Figure 1 ) of c-EXG–TDPP shows very weak and broad PL slightly red-shifted from the linear absorption.…”