Optoelectronic Properties of Hyperbranched Polythiophenes

Abstract

Branched conjugated architectures should possess the advantage of isotropic charge transport compared to conventional linear conjugated polymers, as for example poly(3-hexylthiophene) (P3HT) which is commonly used in organic solar cells. This contribution investigates the optoelectronic properties of branched poly(thiophene)s p3T and p4T synthesized in a straightforward one-pot procedure by oxidative coupling of branched trithiophene and tetrathiophene monomers with FeCl(3). These polymers can be regarded as model systems for ideal amorphous conjugated materials. Optical characterization in solution and in thin films together with cyclic voltammetry data suggests the applicability of these materials for the use in organic solar cell devices. In particular, the HOMO and LUMO levels of the branched polythiophenes are shifted to lower energy values as compared to linear P3HT. Field effect mobilities are in the order of 10(-4) cm(2)/(V s). A first optimization of solar cell devices based on the branched polythiophene materials in combination with PCBM as acceptor resulted in efficiencies of 0.6% with open-circuit voltages being about 30% higher (up to 714 mV) than normally found with P3HT.

Branched Terthiophenes in Organic Electronics: From Small Molecules to Polymers

“…The performance of the synthesized materials was further investigated in bottom gate bottom contact transistors which showed a reasonable field effect charge carrier mobility up to 4.3 × 10 −5 cm 2 V −1 s −1 for P(3T) and 2.5 × 10 −4 cm 2 V −1 s −1 for P(4T) . This was explained by the lower branching density of P(4T) compared to P(3T): In case of P(4T) there is apparently less intramolecular twisting and therefore facilitated intra‐ and intermolecular charge transport.…”

“…With a molecular weight of 7392 g mol −1 the largest reported all‐thiophene dendrimer is the 90T‐dendrimer synthesized in the same group . This monodisperse polymer exhibits an absorption maximum at 387 nm and lowered HOMO and LUMO levels (–5.2 and –3.0 eV, respectively) compared to P3HT (–5.1 and –2.8 eV, respectively) . Power conversion efficiencies up to 1.7% were achieved in combination with PC[61]BM in organic solar cells.…”

“…c) I – V characteristics of BHJ solar cells of the trichloromethane fractions of P(3T) (black circles) and P(4T) (red squares) in combination with PC[61]BM. Adapted with permission . Copyright 2012, American Chemical Society.…”

Optimization of direct arylation polymerization (DArP) through the identification and control of defects in polymer structure

“…they are simply called branching defects. Although the influence of branching on conjugated polythiophenes has been studied previously, the monomers either did not contain alkyl chains or β,β‐linkages instead of α,β‐linkages were studied making the direct comparison with DArP‐produced β‐defects difficult.…”

Synthesis of hyperbranched polythiophenes containing tetrachloroperylene bisimide as bridging moiety for polymer solar cells

“…The PCE values of solar devices based on B-P3HT:PC 60 BM were 0.13-2%. Mangold et al reported two hyperbranched PTs using 2,3-dithienylthiophene or 2,3,5-trithienylthiophene as bridging cores [14]. The In this study, we propose a new approach to synthesize the hyperbranched PT M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT derivatives by introducing perylene bisimide (PBI) or soft alkyl spacer as bridging moieties.…”