Effect of the acceptor moiety on the electrochemical and electrochromic properties of Donor Acceptor Donor polymer films

The aim of this work is to synthesize EC polymers having green or blue colour in the neutral state and transparent oxidized state by using the D A D approach. Two different monomers, diphenylthienopyrazine M1 and diphenylquinoxaline M2 are synthesized. The monomers are successfully electropolymerized to P1 and P2, respectively, by cyclic voltammetry on ITO substrates. The effect of the acceptor moiety on the electrochemical and electrochromic properties of the polymer films is investigated. Both polymers exhibit the characteristic redox couple due to their oxidation reduction at 0.95 V 0.62 V for P1 and at 1.05 V 0.35 V for P2; their doping dedoping reaction is reversible. The two polymers have different optical properties; namely, the phenyl ring in the acceptor unit P2 caused hypsochromic shift. The acceptor moiety affects mainly the LUMO level; specifically, the LUMO level shifted to less negative values by replacing thiophene with phenyl. The electrochromic properties of the polymer films are strongly affected by the acceptor moiety. Polymer P1 changes its colour from green neutral state , to grey intermediate oxidised state , to transparent grey sky blue oxidized state and to lemon green reduced state . Correspondingly, P2 starts from royal blue neutral state , going to blue purple, grey blue and light grey intermediate oxidised states and then to green oxidized state ; additionally, it became also oil green and light blue reduced states . Both polymers are multi coloured and were good candidates for application in electrochromic device

New concepts for the development of active functional polymers for p and n-type OFET- applications

Here we present a concept to improve the field effect transistor performance of P3HT in terms of threshold voltage stability as well as the stability in ambient atmosphere by introducing a strong acceptor dopant in the main polymer chain. In our concept the direct introduction of the acceptor dopant in the polymer main chain ensures the strucural stability against diffusion processes. P3HTs with different contents of acceptor molecules which are fixed linked in the main chain of the polymer, have been synthesized using the McCullough Grignard metathesis method. As acceptor unit has been integrated tetrafluorbenzene (TFB). The introduced dopant amount has been varied in order to obtain an optimum between the processability of the polymers and the resultant transistor performance. Compared to the p-type semionducting polymers the n-type organic materials are markedly less developed. Recently an interesting solution to this task has been proposed in the form of a conjugate d ladder-type poly (benzo-bisimidazobenzo-phenanthroline) (BBL) showing either ambipolar or n-type field effect properties dependent upon the sample preparation and processing. However this rigid-chain ladder polymer is not soluble in the common organic solvents resulting in a rather complicated technological transfer. We report the significant improvement of the BBL-processing utilizing aqueous colloidal dispersions and their OFET-application. The resultant devices demonstrate ambipolar electronic transport with charge carrier mobilities in the range of 10-5 cm2/Vs without specific optimization procedures

n-Type Copolymers with Fluorene and 1,3,4-Heterodiazole Moieties

The successful realization of n-channel field-effect transistors requires the application of semiconducting polymers with high electron mobility (n-type). However, reports on n-type polymers are rather scarce in the literature. Therefore, the development of polymers with suitable electron transport properties is particularly challenging for the synthetic chemistry. Main chain polymers with strong acceptor units, such as 1,3,4-heterodiazoles, are potential candidates for electron transport materials in electronic devices. The fluorene unit is another ring system with interesting physical and chemical properties, which is often used in rigid-rod, main chain polymers. The present work introduces the synthesis of organo-soluble copolymers consisting of alternating fluorene-, 1,3,4-heterodiazole, and, in some cases, additional 2,5-dialkoxyphenylene units in the main chain. The reported synthesis involves modified classical polycondensation as well as the tetrazole route. We demonstrate the possibility of exchanging oxygen in the heteroaromatic ring with sulfur using Lawesson's reagent during the ring closure reaction. An alternative structure of the heterocyclic ring with N-phenyl in the oxygen position is feasible using the tetrazole synthetic route. The chemical and electrochemical properties of the copolyfluorenes are investigated in detail. Some of the synthesized copolyfluorenes have also been used for the preparation of electron-only devices enabling the calculation of the electron mobilities. Further, an organic field-effect transistor (OFET) characteristic was shown

Transparente organische Elektrolumineszenzanordnungen

WO 200129908 A UPAB: 20010607 NOVELTY - An electroluminescent device (I) comprises two transparent electrical contacts (2) mounted on a substrate with a fluorescent polymer solution (1) between the contacts (2) and a sealant (4). USE - The electroluminescent device (I) is useful as a display device. ADVANTAGE - The device is thin and has a high transparency

High triplet energy electron transport side-chain polystyrenes containing dimesitylboron and tetraphenylsilane for solution processed OLEDs

A series of polystyrenes was developed as electron transport materials (ETMs) for solution processed organic light emitting diodes (OLEDs), containing dimesitylboryl (BMes2) and tetraphenylsilanyl in their side-chains. The synthesis and characterisation of the polymers is reported. High triplet energy up to 2.95 eV was obtained for ETMs containing BMes2 and tetraphenylsilanyl. High glass transition temperatures over 180 °C were detected for the series due to the polymer approach, ensuring high thermal stability. The role of both molecular motifs was evaluated in Ir based green OLEDs with all organic layers processed from solution. Similar current efficacies around 30 cd A-1 were measured for the electron-transport polymers, most likely due to the confinement of the LUMO delocalization into the BMes2 unit, leading to similar charge mobility. These results show that incorporation of BMes2 into polymers is an adequate approach for further development of wet-process materials

Polymers with covalently attached dyes - materials for OLEDs and photovoltaics?

An unusual way is presented to obtain a new class of deep red emitting polyurethanes with covalently attached fluorescent dyes. The DCM-dye seems to be a favourable candidate but we had to introduce two reactive hydroxy linker groups into the molecule to enable polymerization. By copolymerization with non-dye molecules the dye content in the main chain can be varied. Red emitting device structures were realized and some of the device properties will be given