Conjugated polymer (CP) aggregates have been the focus of considerable research, as these mesoscopic entities, compared with single CP chains, provide environments more analogous to those present in polymer-based optoelectronics in terms of the complexity of morphology and chain interactions; thereby, such aggregates hold the potential to provide insights into structure–function relationships highly relevant to optoelectronic device efficiency and stability. This review article highlights single-aggregate spectroscopy studies of CP aggregates based on a combination of solvent vapor annealing and single-molecule fluorescence techniques and draws mesoscopic connections between morphology, electronic coupling, and photophysics in CPs. This molecular-level understanding will pave the way for the bottom-up control of optoelectronic properties from the molecular to the device-length scale.
Gaining control over conjugated polymer morphology to improve the performance of organic electronics
Conjugated polymers (CPs) are widely used in various domains of organic electronics. However, the performance of organic electronic devices can be variable due to the lack of precise predictive control over the polymer microstructure. While the chemical structure of CPs is important, CP microstructure also plays an important role in determining the charge-transport, optical and mechanical properties suitable for a target device. Understanding the interplay between CP microstructure and the resulting properties, as well as predicting and targeting specific polymer morphologies, would allow current comprehension of organic electronic device performance to be improved and potentially enable more facile device optimization and fabrication. In this Feature Article, we highlight the importance of investigating CP microstructure, discuss previous developments in the field, and provide an overview of the key aspects of the CP microstructure-property relationship, carried out in our group over recent years.
more »
« less
- Award ID(s):
- 2104234
- NSF-PAR ID:
- 10409823
- Date Published:
- Journal Name:
- Chemical Communications
- Volume:
- 58
- Issue:
- 50
- ISSN:
- 1359-7345
- Page Range / eLocation ID:
- 6982 to 6997
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
Inherently conductive polymers (CPs) can generally be switched between two or more stable oxidation states, giving rise to changes in properties including conductivity, color, and volume. The ability to prepare CP nanofibers could lead to applications including water purification, sensors, separations, nerve regeneration, wound healing, wearable electronic devices, and flexible energy storage. Electrospinning is a relatively inexpensive, simple process that is used to produce polymer nanofibers from solution. The nanofibers have many desirable qualities including high surface area per unit mass, high porosity, and low weight. Unfortunately, the low molecular weight and rigid rod nature of most CPs cannot yield enough chain entanglement for electrospinning, instead yielding polymer nanoparticles via an electrospraying process. Common workarounds include co-extruding with an insulating carrier polymer, coaxial electrospinning, and coating insulating electrospun polymer nanofibers with CPs. This review explores the benefits and drawbacks of these methods, as well as the use of these materials in sensing, biomedical, electronic, separation, purification, and energy conversion and storage applications.more » « less
-
more » « less
Abstract Determining the relative energies of transport states in organic semiconductors is critical to understanding the properties of electronic devices and in designing device stacks. Futhermore, defect states are also highly important and can greatly impact material properties and device performance. Recently, energy‐resolved electrochemical impedance spectroscopy (ER‐EIS) is developed to probe both the ionization energy (IE) and electron affinity (EA) as well as sub‐bandgap defect states in organic semiconductors. Herein, ER‐EIS is compared to cyclic voltammetry (CV) and photoemission spectroscopies for extracting IE and EA values, and to photothermal deflection spectroscopy (PDS) for probing defect states in both polymer and molecular organic semiconductors. The results show that ER‐EIS determined IE and EA are in better agreement with photoemission spectroscopy measurements as compared to CV for both polymer and molecular materials. Furthermore, the defect states detected by ER‐EIS agree with sub‐bandgap features detected by PDS. Surprisingly, ER‐EIS measurements of regiorandom and regioregular poly(3‐hexylthiophene) (P3HT) show clear defect bands that occur at significantly different energies. In regioregular P3HT the defect band is near the edge of the occupied states while it is near the edge of the unoccupied states in regiorandom P3HT.
-
Semiconducting conjugated polymers (CPs) have shown great potential in organic solar cells and organic field-effect transistors (OFETs), due to their tunable electronic and optical properties. In this study, we compare computational predictions of electronic and optical properties of ensembles of cis-polyacetylene (cis-PA) multiple oligomers in two different forms (a) undoped cis-PA and (b) cis- PA doped by phosphorous fluoride (PF6−) via density functional theory (DFT) with hybrid functionals. The comparison of undoped cis-PA under the constraint of injected charge carrier and cis-PA doped by PF6− shows that either doping or injection provides very similar features in electronic structure and optical properties. Doped and injected are similar to each other and different from the pristine, undoped PA. Computed results also indicate that the injection of charge carriers and adding p-type doping into the semiconducting CP model both greatly affect the conductivity. These observations provide a better understanding and practical use of the properties of polyacetylene films for flexible electronic applications.more » « less
-
null (Ed.)Organic electronics technologies have attracted considerable interest over the last few decades and have become promising alternatives to conventional, inorganic platforms for specific applications. To fully exploit the touted potential of plastic electronics, however, other prerequisites than only electronic functions need to be fulfiled, including good mechanical stability, ease of processing and high device reliability. A possible method to overcome these issues is the employment of insulating:semiconducting polymer blends, which have been demonstrated to display favourable rheological and mechanical properties, generally provided by the insulating component, without negatively affecting the optoelectronic performance of the semiconductor. Here, we demonstrate that binary blends comprising the semicrystalline high-density polyethylene (HDPE) in combination with hole- and electron-transporting organic semiconductors allow fabrication of p-type and n-type thin-film transistors of notably improved device stability and, in some scenarios, improved device performance. We observe, for example, considerably lower subthreshold slopes and drastically reduced bias-stress effects in devices fabricated with a hole-transporting diketopyrrolopyrrole polymer derivative when blended with HDPE and significantly enhanced charge-carrier mobilities and shelf life in case of transistors made with blends between HDPE and the electron-transporting poly{[ N , N ′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)2,6-diyl]- alt -5,5′-(2,2′-bithiophene)}, i.e. P(NDI2OD-T2), also known as N2200, compared to the neat material, highlighting the broad, versatile benefits blending semiconducting species with a semicrystalline commodity polymer can have.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D2CC01430K
