High Conductivity in a Nonplanar n-Doped Ambipolar Semiconducting Polymer

Abstract

n-Doping of P(BTP-DPP) with the organometallic dimer (RuCp*mes) 2 , processed through sequential casting, is reported. Maximum conductivities of 0.45 S cm −1 were achieved that are relatively high for n-type semiconducting polymers. Electron paramagnetic resonance spectroscopy, ultraviolet visible spectroscopy, and ultraviolet photoemission spectroscopy are consistent with the introduction of high carrier concentrations by sequential processing, leading to bipolaronic, or otherwise spin-paired carriers. P(BTP-DPP) has glassy ordering in thin films, observed using wide angle X-ray scattering, that allows efficient incorporation of the dopant as a function of processing condition. The changes in electrical conductivity as a function of the dopant concentration are proposed to occur by charge percolation through domains with a mixture of polaronic and bipolaronic carriers.

Enhancing the n‐Type Conductivity and Thermoelectric Performance of Donor–Acceptor Copolymers through Donor Engineering

“…We would like to point out that based on the coherence length and paracrystalline disorder calculations using the GIWAXS data (the calculations are detailed in Figure S22, Supporting Information), PDPF displays similar or even better crystallinity than PDPH , especially in the doped state. Compared with other literature reports stating that low‐crystallinity polymer films are more easily doped, the high doping efficiency observed for PDPF might not be due simply to its better miscibility . In addition, PDPH presents a nearly complete edge‐on orientation, while PDPF presents both edge‐on and face‐on orientations.…”

“…Therefore, the low conductivities of n‐type polymers are mainly caused by the low doping efficiency and consequently the low charge carrier density. Previous studies have demonstrated several effective strategies for enhancing the n‐doping efficiency, such as introducing polar side chains and twisted conjugated units in the polymers, but these modifications could also negatively influence their charge carrier mobility. For instance, after introducing polar side chains, the D–A polymer based on NDI showed a substantially improved conductivity of 0.17 S cm −1 after doping .…”

“…Since microstructures and the host/dopant miscibility might play a big role in the thermoelectric performance, GIWAXS analysis and AFM were performed to study the solid‐state microstructures of the polymer films. Both polymers show high crystallinity and ordered molecular packing in the intrinsic and doped states ( Figure a–f).…”

N‐Type Organic Thermoelectrics of Donor–Acceptor Copolymers: Improved Power Factor by Molecular Tailoring of the Density of States

“…For this reason, growing research efforts are being directed towards developing better n‐type TE materials . So far, advanced conjugated‐backbone designs targeting favorable energetics, high mobility, planar structure, and good host/dopant miscibility have been reported . Moreover, donor–acceptor (D–A) copolymers can show very high charge carrier mobilities .…”

n‐Doping of a Low‐Electron‐Affinity Polymer Used as an Electron‐Transport Layer in Organic Light‐Emitting Diodes

“…[ 15 ] The focus of the present work is to demonstrate the use of solution processing for incorporating [RuCp*Mes] 2 into, and efficiently n‐doping, a low EA polymer. n‐Doping with the ruthenium‐based dimer has been previously demonstrated in solution‐processed polymers; however, it has only been used with hosts that have significantly larger EA (>3.5–4 eV), including P(BTP‐DPP), [ 16 ] P(NDI2OD‐T2), [ 17 ] and FBDPPV, [ 18 ] for which the initial electron transfer from the dimer is considerably less endergonic than that to POPy 2 , leading to facile n‐doping. Here, we employ the polymer poly[(9,9‐dioctylfluorene‐2,7‐diyl)‐ alt ‐(benzo[2,1,3]thiadiazol‐4,7‐diyl)] (F8BT) (Figure 1b), with a low EA equal to 2.8 eV and which is therefore much more challenging to n‐dope.…”