Synthetic Principles for Bandgap Control in Linear pi-Conjugated Systems.

In this paper it is demonstrated that the characteristics of light‐emitting diodes based upon MEH‐PPV [more fully known as poly(2‐methoxy,5‐(2’‐ethyl‐hexoxy)‐1,4‐phenylene‐ vinylene)] are determined by tunneling of both the holes and the electrons through interface barriers caused by the band offset between the polymer and the electrodes. It is shown that manipulating these offsets can control the useful operating voltage of the device as well as its efficiency. A model is developed that clearly explains the device characteristics of a wide range of diodes based upon MEH‐PPV. The turn‐on voltage for an ideal device is shown to be equal to the band gap, i.e., 2.1 eV for MEH‐PPV, and is slightly lower at 1.8 eV for an indium‐tin oxide/MEH‐PPV/Ca device. If there is a significant difference in the barrier height, the smaller of the two barriers controls the I–V characteristics, while the larger barrier determines the device efficiency. In indium‐tin‐oxide/MEH‐PPV/Ca devices, the barrier to hole injection is ...

Carrier tunneling and device characteristics in polymer light‐emitting diodes

All-polymer and paper-based energy storage devices have significant inherent advantages in comparison with many currently employed batteries and supercapacitors regarding environmental friendliness, flexibility, cost and versatility. The research within this field is currently undergoing an exciting development as new polymers, composites and paper-based devices are being developed. In this report, we review recent progress concerning the development of flexible energy storage devices based on electronically conducting polymers and cellulose containing composites with particular emphasis on paper-based batteries and supercapacitors. We discuss recent progress in the development of the most commonly used electronically conducting polymers used in flexible device prototypes, the advantages and disadvantages of this type of energy storage devices, as well as the two main approaches used in the manufacturing of paper-based charge storage devices.

Toward Flexible Polymer and Paper‐Based Energy Storage Devices

The characterization of rectifying heterojunctions (diodes) fabricated from a semiconducting polymer, a soluble derivative of poly(phenylene‐vinylene), and buckminsterfullerene, C60, are reported. Rectification ratios in the current versus voltage characteristics exceed 104. When illuminated, the devices exhibit a large photoresponse as a result of photoinduced electron transfer across the heterojunction interface from the semiconducting polymer (donor) onto C60 (acceptor). The photodiode and photovoltaic responses are characterized. Photoinduced electron transfer across the donor‐accepted rectifying heterojunction offers potential for photodetector and for solar cell applications.

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Semiconducting polymer‐buckminsterfullerene heterojunctions: Diodes, photodiodes, and photovoltaic cells

Simutaneously high open circuit voltage and high short circuit current density is a big challenge for achieving high efficiency polymer solar cells due to the excitonic nature of organic semdonductors. Herein, we developed a trialkylsilyl substituted 2D-conjugated polymer with the highest occupied molecular orbital level down-shifted by Si–C bond interaction. The polymer solar cells obtained by pairing this polymer with a non-fullerene acceptor demonstrated a high power conversion efficiency of 11.41% with both high open circuit voltage of 0.94 V and high short circuit current density of 17.32 mA cm−2 benefitted from the complementary absorption of the donor and acceptor, and the high hole transfer efficiency from acceptor to donor although the highest occupied molecular orbital level difference between the donor and acceptor is only 0.11 eV. The results indicate that the alkylsilyl substitution is an effective way in designing high performance conjugated polymer photovoltaic materials. In organic photovoltaics, non-fullerene acceptors relax matching rules and allow for the development of new donor polymers. Here, Bin et al. design a donor polymer and obtain high photoconversion efficiencies despite the low energy offset for hole transfer between the acceptor and the donor.

https://scholarworks.unist.ac.kr/bitstream/201301/20892/1/ncomms13651.pdf

11.4% Efficiency non-fullerene polymer solar cells with trialkylsilyl substituted 2D-conjugated polymer as donor.

Homopolymers and copolymers of 3-alkylthiophenes incorporating alkyl groups equal to or greater than butyl in size can be handled in solution and form highly conducting, environmentally-stable compositions on doping.

Highly conducting, soluble, and environmentally-stable poly(3-alkylthiophenes)

The electronic and electrochemical properties of poly(p‐phenylene vinylene), poly(thienylene vinylene), and their derivatives with electron donating moieties such as methyl, methoxy, and ethoxy are studied using the newly developed electrochemical potential spectroscopy (ECPS) and optical spectroscopy. It is shown that electrochemically derived band gaps agree well with band gap values obtained from optical measurements. Substitution with electron donating groups substantially lowers the ionization potentials and band gaps. A similar effect can be attributed to the incorporation of a vinylene linkage between rings of the polymer backbone. Our results imply that through a proper choice of substituents and backbone structure one can adjust the electrochemical potentials over a wide range as well as red shift the absorption edge of these polymers. In the case of the alkoxythienylene vinylenes the absorption edge is shifted through the visible range of the spectrum into the near infrared (NIR) yielding polyme...

The electronic and electrochemical properties of poly(phenylene vinylenes) and poly(thienylene vinylenes): An experimental and theoretical study

High molecular weight, free-standing films of poly(2,5-thienylene vinylene) are readily prepared via a soluble precursor polymer and reach conductivities as high as 62 S cm–1 on doping.

Highly-conducting, poly(2,5-thienylene vinylene)prepared via a soluble precursor polymer

Facile preparation of electrically conductive poly(isothianaphthene)

Alkoxy substituted poly(thienylene vinylenes) are conductive, electrochemically reversibly acceptor and donor dopable, and have ionization potentials and band gaps that are significantly less than those of the parent, unsubstituted polymer.

Kwan Yue Jen

Papers

Highly conducting, soluble, and environmentally-stable poly(3-alkylthiophenes)

The electronic and electrochemical properties of poly(phenylene vinylenes) and poly(thienylene vinylenes): An experimental and theoretical study

Highly-conducting, poly(2,5-thienylene vinylene)prepared via a soluble precursor polymer

Facile preparation of electrically conductive poly(isothianaphthene)

Optical, electrochemical, and conductive properties of poly(3-alkoxy-2,5-thienylene vinylenes)