Modelling polymers with side chains: MEH-PPV and P3HT

Lavarda

2014

Mat. Res.

Computational modeling studies of conjugated polymers have been shown to present many challenges. Dne such challenge is to find ways to reduce the computational cost for these studies without compromising the quality of the results. An approach longly used in the literature for this purpose is replacing long alkyl side chains (with six or more carbons) with a methyl group. This work reports on a theoretical study conducted with the conjugated polymer poly(3-hexylthiophene), which contains a hexyl side chain attached to the monomer, to verify the influence of the size of the alkyl side chain on its electronic structure. The results indicated that, for polymers containing long alkyl side chains, replacement with a propyl group offered full saturation of all properties under review, showing it to be a good approach.

Section: Calculation Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Effect of the length of alkyl side chains in the electronic structure of conjugated polymers

Lavarda

2014

Mat. Res.

Copolymers with similar comonomers: Tuning frontier orbital energies for application in organic solar cells

Polymer Engineering & Sci

Lavarda

2016

Today, there is an intense search for new electron donor polymers for the active layers of organic solar cells. The synthesis of copolymers, in which there is a mix of electron donor monomers with others that are electron acceptors, is a currently employed approach that is used to obtain new polymers with more interesting electronic properties. Usually, the comonomers have a very different structure and the energies of the frontier electronic levels are unpredictable. We demonstrate in this work that the approach of using similar comonomers allows for the provision of copolymers with predictable energies of the frontier electronic levels. We explore the properties of copolymers consisting of monomers of poly(3-hexylthiophene), poly(3-hexyloxythiophene) and some poly(3-hexylthiophene) derivatives. The results indicate that the copolymers have intermediate frontier orbital energies when compared to the parent homopolymers and these energies are easy to predict. This approach is an alternative way of designing a copolymer with favorable tuning of the energies of the frontier electronic levels and is supported by experimental evidence. POLYM. ENG. SCI., 56:479-487, 2016. V C 2016 Society of Plastics Engineers INTRODUCTIONToday, there is a wide spectrum of important applications for organic conducting polymers (OCPs) in organic electronics [1][2][3][4][5]. Therefore, a control mechanism for the energies of the highest occupied and lowest unoccupied molecular orbitals (E HOMO and E LUMO ), the bandgap E LUMO -E HOMO (DE HL ) and optical properties is desirable in order to optimize the various types of devices [6,7]. These properties are crucial to the development of the promising technology of organic solar cells (OSC) [8,9].Currently, the scientific community has focused on two different ways of improving the efficiency of solar cells by controlling the electronic properties of OCPs [8][9][10]. The first adopted strategy has been to adjust the frontier electronic energy levels of the donor material to the levels of a given acceptor material. Normally, this is achieved through the design of OCPs with a lower E HOMO in order to increase the open-circuit voltage in the device (V OC ) [8][9][10][11][12][13]. The use of chemical substitutions is an effective way of implementing this change in the energies of the frontier orbitals, but with no major changes in the bandgap, as recently shown for poly(3-hexylthiophene) (P3HT) derivatives [14,15]. The second strategy is based on the design of new OCPs with a low bandgap in order to collect more photons of the solar spectrum and to increase the electric current in the device [8-10, 16, 17]. The donor-acceptor (DA) concept, which is the most frequently employed approach, is the synthesis of copolymers in which there is a mix of electron donor monomers with others that are electron acceptors [7,10]. Usually, the monomers have a very different structure and the resulting OCPs demonstrate a lower bandgap, but also a significant worsening in the other properties [18] as a decrease i...

Theoretical evaluation of chemical substitutions along the main chain of poly(3‐hexylthienylene‐vinylene) for solar cell applications

Roldao

Sato

et al. 2017

Polymer International

In order to improve the efficiency of bulk‐heterojunction organic solar cells, one can try to optimize the active layer through the use of new materials that provide improvements in the parameters that influence the final efficiency of a device. The use of chemical substitutions in organic materials already used in these devices seems to be an efficient methodology to obtain new materials with better intrinsic properties. Based on this idea, in this work is investigated theoretically, by methods of electronic structure calculation, a set of 143 poly(3‐hexylthienylene‐vinylene) (P3HTV) derivatives for application in active layers of organic solar cells as electron donor materials; the chemical modifications were performed on the thiophene ring and the vinyl segment of P3HTV. The results show that it is possible to obtain several new derivatives with better optical and electronic properties than those of P3HTV. The derivative substituted with trifluoromethyl on the vinyl segment is one of the most promising for use in active layers, when combined with phenyl‐C61‐butyric‐acid‐methyl‐ester as electron acceptor material. An equation to predict the electronic properties of P3HTV derivatives when using more than one chemical substitution is also proposed, which is corroborated by the theoretical calculations. © 2017 Society of Chemical Industry